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MP Board Class 9th Maths Solutions Chapter 9 Areas of Parallelograms and Triangles Ex 9.2

Question 1.
In fig. given below, ABCD is a parallelogram, AE ⊥ DCand CF ⊥ AD. If AB = 16 cm, AE = 8 cm and CF = 10 cm, find AD.

Solution:
ar (ABCD) = AE x DC ….(i)
ar (ABCD) = AD x CF ….(ii)
From (i) and (ii), we get
AE x DC = AD x CF
⇒ AE x AB = AD x CF (∵ AB = DC)

8 x 16 = AD x 10
\(\frac{8×16}{10}\) = AD
\(\frac{128}{10}\) = AD
AD = 12.8 cm.

Question 2.
If E, F, G and H are respectively the mid-points of the sides of a parallelogram ABCD, show that ar (EFGH) \(\frac{1}{2}\) = ar (ABCD)
Solution:
Given
ABCD is a ∥^gm E, F, G, H, are the mid-points of AB, BC, CD and DA respectively.

To prove:
ar (EFGH) = \(\frac{1}{2}\) ar (ABCD)
Construction: Join GE.
Proof:
ABCD is a ∥gm
∴ AB ∥ DC and AB = DC
⇒ \(\frac{1}{2}\)AB ∥ \(\frac{1}{2}\)DC and \(\frac{1}{2}\) AB = \(\frac{1}{2}\) DC
AE ∥ DG and AE = DG
∴ AEGD is a parallelogram.
Similarly BCGE is also a parallelogram.
∥gm AEGD and AEGH both lie on the same base EG and are between the same parallels AD and EG.
ar (EGH) = \(\frac{1}{2}\) ar {AEGD) …(1)
Similarly ar {GEF) = \(\frac{1}{2}\) ar {BCGE) …(2)
Adding (1) and (2), we get
ar (EGH) + ar (GEF) = ar (AEGD) + \(\frac{1}{2}\) ar {BCGE)
ar (EFGH) ar {EFGH) = \(\frac{1}{2}\) [ar (AEGD) + ar (BCGE)]

Question 3.
P and Q are any two points lying on the sides DC and AD respectively of a parallelogram ABCD. Show that ar (APB) = ar (BQC).
Solution:
Given:
ABCD is a ∥^gm
To prove:
ar (APB) = ar (BQC)..
Proof:
∆APB and ∥^gm ABCD lie on the same base BC and are between the same parallels AB and DC.

ar(APB) = \(\frac{1}{2}\) ar (ABCD)
∆BQC and ∥^gm ABCD lie on the same base BC and are between the same parallels BC and AD.
ar (BQC) = \(\frac{1}{2}\) ar (ABCD) …(2)
From (1) and (2), we get
ar (APB) = ar (BQC)

Question 4.
In Fig. given below, P is a point in the interior of a parallelogram ABCD, Show that

1. ar (APB) + ar (PCD) = \(\frac{1}{2}\) ar (ABCD)
2. ar (APD) + ar (PBC) = ar (APB) + ar (PCD)

[Hint: Thorough P, draw a line parallel to AB.]
Solution:
Given:
P is any point in the interior of ∥^gm ABCD.
To prove:

1. ar (APB) + ar (PCD) \(\frac{1}{2}\) ar (ABCD)
2. ar (APD) + ar (PBC) ar (APB) + ar (PCD)

1. Construction:
Draw a line EF passing through point P parallel to AB.
Proof:
AB ∥EF (By construction) …(1)
AB ∥ DC (∵ ABCD is a ∥gm) …(2)
EF ∥ DC [From (1) and (2)]

In quadrilateral ABFE, AB ∥ EF and AE ∥ BF (∵ AD ∥ BC)
∴ ABFE is a ∥gm
∆ APB and ∥gm ABEF lie on same base base AB and are between the same parallels AB and EF.
ar (APB) = \(\frac{1}{2}\) ar (ABFE) …. (A)
Similarly, ar (PCD) = \(\frac{1}{2}\) ar (DCFE) …(B)
Adding (A) and (B), we get
ar (APB) + ar (PCD) = \(\frac{1}{2}\) ar (ABFE) + \(\frac{1}{2}\) (DCFE)
= \(\frac{1}{2}\) [ar (ABFE) + ar (DCFE)]
= \(\frac{1}{2}\) ar (ABCD) …(3)

2. Construction:
Draw a line GH passing through point P parallel to AD.
Proof:
AD ∥ GH (by construction) …(4)
AD ∥ BC (∵ ABCD is a ∥^gm) …(5)
GH ∥ BC [From (4) and (5)]
In quadrilateral ADHG,
AD ∥ GH (by construction)
and AG ∥ DH (∵ AB\\DC)
∴ ADHG is a parallelogram.
∆APD and ∥gm ADHG lie on the same base AD and lie betweeiwthe same parallels AD and GH.
ar(APD) = \(\frac{1}{2}\) ar (ADHG) …(6)
Similarly, ar (BCP) = \(\frac{1}{2}\) ar (BCHG) …(7)
Adding (6) and (7), we get
ar (APD) + ar (BCP) = \(\frac{1}{2}\) ar (ADHG) + \(\frac{1}{2}\) ar (BCHG)
= \(\frac{1}{2}\) ar (ADHG) + ar (BCHG)
= \(\frac{1}{2}\) [ar (ADHG) + ar (BCHG)]
= \(\frac{1}{2}\) ar (ABCD) …(8)
From (3) and (8), we get
ar (APB) + ar (PCD) = ar (APD) + ar (BCP)

Question 5.
In Fig. given below PQRS and ABRS are parallelograms and X is any point on side BR. Show that

1. ar (PQRS) = ar (ABRS)
2. ar (AZS) = \(\frac{1}{2}\) ar (PQRS)

Solution:
Given
PQRS and ABRS are H801 and X is any point on side BR.
To prove:

1. ar (PQRS) = ar (ABRS)
2. ar (AXS) \(\frac{1}{2}\) ar (PQRS)

Proof:
1. ∥^gm PQRS and ABRS lie on the same base SR and are on the same parallels SR and PB.
∴ ar (PQRS) = ar (ABRS) …(i)

2. D AXS and ∥^gm ABRS lie on the same base AS and are on the same parallels AS and BR.
ar (∆ AXS) = \(\frac{1}{2}\) ar (ABRS) …(ii)

From (i) and (ii), we get
ar (AXS) = \(\frac{1}{2}\) ar (PQRS)

Question 6.
A farmer was having a field in the form of a parallelogram PQRS. She took any point A on RS and joined it to points P and Q. In how many parts the fields is divided? What are the shapes of these parts? The farmer wants to sow wheat and pulses in equal portions of the field separately. How should she do it?
Solution:
The field will be divided in three parts. The shapes of three parts are triangles.
Given:
PQRS is a ∥^gm
To prove:
ar (APQ) = ar (APS) + ar (AQR)
Construction:
Draw a line AB ∥ SP.
Proof:
∆APQ and ∥^gm PQRS are on the same base PQ and are between the same parallels PQ and SR.

ar (PQRS) = \(\frac{1}{2}\) ar (PQRS)
⇒ 2ar (APQ) = ar (PQRS)
2ar (APQ) = ar (APS) + ar (APQ) + ar (AQR)
2ar (APQ) – ar (APQ) = ar (APQ) ar (AQR)
ar (APQ) = ar (APS) + ar (AQR)

MP Board Class 9th Maths Solutions

MP Board Class 7th Science Solutions Chapter 15 Light

Light Intex Questions

Question 1.
Paheli wants to know, what makes things visible to us? Boojho thinks that objects are visible only when light reflected from them reaches our eyes. Do you agree with him?
Answer:
Yes.

Question 2.
Boojho noted in his notebook: Is it not surprising that my image is of the same size as me whether the mirror is small or large?
Answer:
Yes.

Question 3.
Paheli made a note in her notebook: In a plane mirror the image is formed behind the mirror. It is erect, of the same size and is at the same distance from the mirror as the object is in front of it?
Answer:
Yes.

Question 4.
Boojho saw an ambulance on the road. He was surprised to see that the word ‘AMBULANCE’ in front was written in a strange manner?
Answer:
When the driver of a vehicle ahead of an ambulance looks in her/his rear view mirror, he/she can read ‘AMBULANCE’ written on it and give way to it. It is the duty of every one of us to allow an ambulance to pass without blocking its way.

Activities

Activity – 1
Write down the letters ABC on a piece of paper with sketch pen and look at its image in a plane mirror. Then find out which letters look the same as on the paper and which letters look different (fig.) Try to write these letters as seen in the mirror
Answer:

Activity – 2
Take a red book and allow white light to fall on it (fig)
Answer:
The color of the book is due to the red color which gets reflected from the book, i.e., it reflects only red color while it absorbs all the other colours of white light. A rose is red because it reflects only red light.

Light Text Book Exercises

Question 1.
Fill in the blanks:

1. An image that cannot be obtained on a screen is called ………………………..
2. Image formed by a convex ……………………….. is always virtual and smaller in size.
3. An image formed by a …………………….. mirror is always of the same size as that of the object.
4. An image which can be obtained on a screen is called a ………………………….. image.
5. An image formed by a concave ………………………. cannot be obtained on a screen.

Answer:

1. Virtual image
2. Mirror
3. Plane
4. Real
5. Lens

Question 3.
Match the items given in of Column I with one or more items Column II:

Answer:

1. (a) – (v)
2. (b) – (ii)
3. (c) – (i)
4. (d) – (iii)
5. (e) – (vi)

Question 4.
State the characteristics of the image formed by a plane mirror?
Answer:
The characteristics of the image formed by a plane mirror are:

1. It forms an erect image.
2. It forms a virtual image.
3. It forms the image behind the mirror.
4. The size of the image is same as that of the object.
5. It forms the image at the same distance behind the mirror as the object stands infront of it.

Question 5.
Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings?
Answer:
Letters like A, H, I, M, O, T, U, V, and W.

Question 6.
What is a virtual image? Give one situation where a virtual image is formed?
Answer:
The image which cannot be taken on a screen is called a virtual image. For example, when some object is placed very close to the concave mirror we do not get any image of that object on the white screen placed behind the mirror. This type of image is known as virtual image.

Question 7.
State two differences between a convex and a concave lens?
Answer:
Convex lens:

1. These are thick at middle and thin at edge.
2. They can form magnified image.

Concave lens:

1. These are thin at middle and thick at edge.
2. The image formed by these lens are always diminished in size.

Question 8.
Give one use each of a concave and convex mirror?
Answer:
Use of convex mirror:
It is used in vehicles as rear view mirror.

Concave mirror:
It is used by dentists to examine is used in vehicles as rear view mirror.

Question 9.
Which type of mirror can form a real image?
Answer:
Concave mirror.

Question 10.
Which type of lens forms always a virtual image?
Answer:
Concave lens.

Choose the correct option in questions 11 – 13:

Question 11.
A virtual image larger than the object can be produced by a –

1. Concave lens
2. Concave mirror
3. Convex mirror
4. Plane mirror

Answer:
2. concave mirror

Question 12.
David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be –

1. 3 m
2. 5 m
3. 6 m
4. 8 m.

Answer:
3. 6 m

Question 13.
The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be –

1. 1 m/s
2. 2 m/s
3. 4 m/s
4. 8 m/s.

Answer:
3. 4 m/s

Extended Learning – Activities and Projects

Question 1.
Play with mirror? Write your name with a sketch pen on a thin sheet of paper, polythene or glass. Read your name on the sheet while standing infront of a plane mirror. Now look at your image in the mirror?
Answer:
Do yourself

Question 2.
A burning candle in water? Take a shoe box, open on one side. Place a small lighted candle in it. Place a clear glass sheet Fig- Candle burning in water (roughly 25 cm x 25 cm) infront of this candle (Fig.). Try to locate the image of the candle behind the glass sheet. Place a glass of water at its position. Ask your friends to look at the image of the candle through the sheet of glass. Ensure that candle is not visible to your friends. Your friends will be surprised to see the candle burning in water. Try to explain the reason?
Answer:
Do yourself.

Question 3.
Make a rainbow?
Try to make your own rainbow. You can try this project in the morning or in the evening. Stand with your back towards the sun/ Take a hosepipe or a water pipe used in the garden. Make a fine spray in front of you. You can see different colours of rainbow in the spray?
Answer:
Do yourself.

Question 4.
Visit a laughing gallery in some science centre or a science park or a village mela. You will find some large mirrors there. You can see your distorted and funny images in these mirrors. Try to find out the kind of mirrors used there?
Answer:
Do yourself.

Question 5.
Visit a nearby hospital. You can also visit the clinic of an ENT specialist, or a dentist. Request the doctor to show you the mirrors used for examining ear, nose, throat and teeth. Can you recognise the kind of mirror used in these instruments?
Answer:
Do yourself.

Question 6.
Role play?
Here is a game that a group of children can play. One child will be chosen to act as object and another will act as the image of the object. The object and the image will sit opposite to each other. The object will make movements, such as raising a hand touching an ear, etc. The image will have to make the correct movement following the movement of the object. The rest of the group will watch the movements of the image. If the image fails to make the correct movement, she/he will be retired. Another child will take her/his place and the game will continue. A scoring scheme can be introduced. The group that scores the maximum will be declared the winner?
Answer:
Do yourself.

Light Additional Important Questions

Objective Type Questions

Question 1.
Choose the correct alternative:

Question (a)
Formation of shadows suggests that light travels in –
(a) vacuum
(b) straight lines
(c) dark rooms
(d) None of these.
Answer:
(b) straight lines

Question (b)
A smooth polished surface which can return back the rays of light into the same medium is called –
(a) mirror
(b) lens
(c) prison
(d) None of these.
Answer:
(a) mirror

Question (c )
The phenomenon of bouncing back of the rays of light into the same medium is called –
(a) reflection
(b) refraction
(c) scattering
(d) None of these.
Answer:
(a) reflection

Question (d)
If the image cannot be taken on the screen, it must be –
(a) real
(b) virtual
(c) real or virtual
(d) None of these.
Answer:
(b) virtual

Question (e)
A spherical mirror with its reflecting surface on the outside is a –
(a) plane mirror
(b) convex mirror
(c) concave mirror
(d) None of these.
Answer:
(b) convex mirror

Question (f)
The mirror which is used as rear – view mirror in cars and scooters is, by nature –
(a) plane
(b) convex
(c) concave
(d) None of these.
Answer:
(b) convex

Question (g)
An image that can be obtained on a screen is –
(a) virtual
(b) real
(c) both real and virtual
(d) None of these.
Answer:
(b) real

Question (h)
The image produced by a plane mirror is –
(a) small
(b) real
(c) inverted
(d) equal size virtual and erect.
Answer:
(d) equal size virtual and erect.

Question (i)
In the formation of rainbow the altitude of the sun should be between or less than –
(a) 40° to 42°
(b) 42° to 44°
(c) 41° to 43°
(d) 0° to 40°.
Answer:
(a) 40° to 42°

Question (j)
White light comprises of ……………………… colours?
(a) 7
(b) 5
(c) 3
(d) 8.
Answer:
(a) 7

Question (k)
Which of the following can be used to prove that light consists of seven colours?
(a) plane mirror
(b) convex lens
(c) Newton’s disc
(d) None of these.
Answer:
(c) Newton’s disc

Question (l)
If the speed of rotation of Newton’s colour disc is fast enough, the various colours would blend and produce –
(a) white light
(b) red light
(c) no light at all
(d) green light.
Answer:
(a) white light

Question (m)
Primary colours are –
(a) red, blue, yellow
(b) red, yellow, magenta
(c) red, blue, green
(d) None of these.
Answer:
(c) red, blue, green

Question (n)
Which color is produced by mixing of blue and green?
(a) cyan
(b) magenta
(c) yellow
(d) blue.
Answer:
(a) cyan

Question 2.
Fill in the blanks:

1. The surface of water can act like a mirror and change the path of …………………………
2. An image formed by a plane mirror is erect and of the same size as the ……………………
3. The curved shining surface of a spoon acts as a ……………………
4. The inner surface of the cut ball is called and the outer surface is called ………………………
5. Concave mirrors are also used by dentists to see an enlarged image of the ………………………
6. The reflectors of tourches, headlights of cars and scooters are ……………………….. in shape.
7. The magnifying glass is actually a type of a ……………………………..
8. A convex lens is also called ………………………….. lens.
9. A concave lens is also called ……………………….. lens.
10. The rainbow has ………………………… colours.
11. The process of splitting up of white light into different colours is called ……………………
12. In a common rainbow the …………………………. colour is observed in the inner fringe and ………………………. on the outer fringe.

Answer:

1. Light
2. Object
3. Mirror
4. Concave, convex
5. Teeth
6. Concave
7. Lens
8. Converging
9. Diverging
10. Seven
11. Dispersion of light
12. Violet, red.

Question 3.
Which of the following statements are true (T) or false (F):

1. A shining stainless steel’spoon or plate can change the direction of light.
2. In a plane mirror only sides are interchanged.
3. The common example of a curved mirror is a spherical mirror.
4. The reflecting surface of the bell is convex.
5. Convex mirrors can form images of objects spread over a large area.
6. The lenses are not transparent.
7. A concave lens always forms erect, virtual and smaller image than the object.
8. A rainbow is seen as a large arc in the sky with many colours.
9. The sunlight consists of five colours.
10. The white light is composed of seven colours.

Answer:

1. True
2. Ture
3. True
4. True
5. True
6. False
7. True
8. True
9. False
10. True

Light Very Short Answer Type Questions

Question 1.
Give the names of four different sources of light?
Answer:
The four different sources of light are:

1. Sun
2. Stars
3. Moon
4. Firefly.

Question 2.
How does light travel from one point to the other?
Answer:
Light travel from one point to the other in straight line.

Question 3.
How can we change the direction of the light?
Answer:
We can change the direction of light by the phenomenon called reflection.

Question 4.
What is refraction?
Answer:
Bending of light when it travels from one medium to another is called refraction.

Question 5.
Define concave mirror?
Answer:
In a spherical mirror, of the reflecting surface is on the inside, it is called a concave mirror.

Question 6.
Define convex mirror?
Answer:
In a spherical mirror, if the reflecting surface is on the outside, it is called a convex mirror.

Question 7.
Define reflection of light?
Answer:
The phenomenon of turning back of light into the same medium on striking a polished surface is called reflection of light.

Question 8.
Define real image?
Answer:
An image that can be captured on a screen is called a real image.

Question 9.
Define virtual image?
Answer:
An image which cannot be captured on a screen is called a virtual image.

Question 10.
Define plane mirror?
Answer:
A plane polished surface capable of reflecting light regularly is known as a plane mirror.

Question 11.
How is the word AMBULANCE written on an ambulance?
Answer:

Question 12.
What happens when light falls on a mirror?
Answer:
The mirror reflects the direction of light that falls on it.

Question 13.
Why is the sky blue?
Answer:
The blue color of the sky is the result of the white light from the sun being separated into different colours.

Question 14.
Where do the different colours come from?
Answer:
All Colours came from light.

Question 15.
Define dispersion?
Answer:
The branching of white light into various colours is called dispersion of light.

Question 16.
How rainbows are formed?
Answer:
Rainbows are formed by sunlight falling on rain drops.

Question 17.
Have you ever seen a rainbow in the sky?
Answer:
Yes.

Question 18.
Does the white light consists of seven colours?
Answer:
Yes.

Light Short Answer Type Questions

Question 1.
Name the four features of the image formed by a plane mirror?
Answer:
The four features of the image formed by a plane mirror are:

1. The image formed by a plane mirror is as far behind the mirror as the object is in front of it.
2. It is virtual.
3. It is exactly of the same size and shape.
4. It is erect but laterally inverted.

Question 2.
What is the real image of an object?
Answer:
Real image is that image where the rays of light actually pass hence, it can be taken on the screen and is always inverted.
For example: image formed by pinhole camera, convex lens and concave mirror etc.

Question 3.
Name two situations in which the real image of an object is formed?
Answer:

1. When the object is at infinity.
2. When the object is at centre of curvature.

Question 4.
Give one use each Of concave and convex mirrors?
Answer:
Use of concave mirror:

1. They are used in reflected of car, head-lights and search lights.
2. They are used as shaving mirrors.
3. They are used in telescopes.

Use of convex mirrors:

1. They are used in automobiles by the drivers for seeing the erect images of the traffic.

Question 5.
What is virtual image? Give one example of virtual image?
Answer:
Virtual image is that image where the rays of light appear to intersect hence, it can only be seen, but it cannot be taken on the screen and is always erect. For example, image formed by plane mirror convex mirror and concave lens etc.

Question 6.
State two uses of concave mirror?
Answer:
The two uses of concave mirror are :

1. Concave mirrors are used as reflectors in car head-lights, search lights, torches and table lamps.
2. Concave mirrors are used by doctors to concentrate light on nose, ear, eyes etc.

Question 7.
Mention some of the uses of plane mirror?
Answer:
Uses of plane mirror are:

1. In hair cutting saloons, shops and at home.
2. For constructing periscope.
3. For constructing kelodoscope.

Question 8.
How will you come to know that the mirror given to you is a concave or convex?
Answer:
In the concave surface the polish is done on its outer surface and the inner surface is shining. If we bring it closer to our face the later will look very big. In a convex mirror the polish is done on the inner surface and then outer side is shining. In this mirror our face will always appear to be shorter.

Question 9.
Draw a ray diagram to explain the formation of a virtual image of a point source of light in a plane mirror?
Answer:
The image of a point object formed by a plane mirror.

Question 10.
In figure, complete the image of the coin after reflection at the surfaces of both the mirrors?

Fig. A ray diagram for formation of image by a pair of inclined mirrors.

Question 11.
Differentiate between real and virtual image formed by mirrors?
Answer:
Difference between real and virtual image:
Real image:

1. It can be obtained on a screen.
2. It is inverted.
3. It is obtained on the same side of mirror as the object.
4. Rays converge at a point to form the image.

Virtual image:

1. It cannot be obtained on a screen.
2. It is erect.
3. It is formed always behind the mirror.
4. Rays appear to diverge from a point where the image is formed.

Question 12.
Draw concave and convex mirrors?
Answer:

Question 13.
Draw convex and concave lens?
Answer:

Question 14.
Differentiate between reflection and refraction?
Answer:
Differences between reflection and refraction:
Reflection:

1. The speed of light remains the same.
2. The incident ray and the reflected ray travel in the same media.
3. In reflection the ray of light gets reflected back into the same medium.

Refraction:

1. The speed of light varies as it travels from one medium to another.
2. The incident ray and the refracted ray travel in different media.
3. In the refraction the ray of light bends at the surface of separation between the two media.

Question 15.
Define mixing of colours? What is the color of the object as the red and green glasses?
Answer:
When two colours mix or overlap, a third color is produced. Thus, red + green = yellow; red + blue = magenta; red + blue + green = white and so on. In fact, any color can be obtained by the combination of red, green and blue which are called the primary colours. The colours so produced. From them are called secondary colours. The mixing of colours can be shown with the help of the diagram given in fig.

Light Long Answer Type Questions

Question 1.
Explain the image formation in plane mirror?
Answer:
A mirror with a plane surface is called a plane mirror. The ordinary mirror we use is a plane mirror. Formation of image is one of effects on reflection of light. The image is seen behind the mirror and it is of the same size as the object. The distance from the object to the mirror and the distance between the mirror and the image are equal. In the plane mirror the right side of the object appears to be left side of the image, and the left side of the object appears to be the right side of the image. This inversion of sides is known as lateral inversion.

Question 2.
Define Newton’s experiment?
Answer:
Newton’s Experiment:
The idea that sunlight consists of several colours was first put forward by Sir Isaac Newton. He passed a narrow beam of light into a prism. The light that emerged from the prism was found to be coloured as in a rainbow. He gave the name spectrum to this coloured patch of light. The spectrum was seen to consist of seven colours of light – violet, indigo, blue, green, yellow, orange and red. The various colours found in white light can be easily remembered as VIBGYOR. The process of splitting up of white light into different colours is called dispersion of light.

Question 3.
Explain rainbow?
Answer:
Rainbows are formed by sunlight falling on rain drops. The rainbow is always observed with the back towards the sun. The rainbow is formed when rain drops owing to refraction and internal reflection produce deviation and dispersion into seven colours of the sunlight falling on them. The rainbows are visible only when the altitude of the sun is less than 42°.

A full rainbow can be seen from an aeroplane flying at higher altitudes. It is a matter of common observation that when one looks at a spray of water on which sun shines, rainbows are seen. When you look at the water falls with the sun shining at your back, a circular rainbow will be seen. In a common rainbow (primary rainbow) the violet color is observed in the inner fringe and red on the outer fringe.

Question 4.
How will you show that combining seven colours, we get white light?
Answer:
Take a circular cardboard disc of about 10 cm diameter. Divide this disc into seven segments. Paint the seven rainbow colours on these segments as shown in Fig. (a). A small hole is made at the center of the disc. Fix the disc loosely on the tip of a refill of a ball pen. Ensure that the disc rotates freely [Fig.(a)]. Rotate the disc in the daylight. When the disc is rotated fast, the colours get mixed together and the disc appears to be whitish [Fig. (b)]. This disc is popularly known as Newton’s disc.

MP Board Class 7th Science Solutions

MP Board Class 9th Science Solutions Chapter 13 Why do we Fall Ill

Why do we Fall Ill Intext Questions

Why do we Fall Ill Intext Questions Page No. 178

Question 1.
State any two conditions essential for good health.
Answer:
Two conditions essential for good health are:

1. Balanced diet and good nutrition.
2. Good social surrounding and economic wellness.

Question 2.
State any two conditions essential for being free of disease.
Answer:
Two conditions essential for being disease – free are:

1. Personal and community hygiene.
2. Proper diet and economic growth.

Question 3.
Are the conditions essential for maintaining good health and being free of diseases same or different? Why?
Answer:
Yes, to some extent they are the similar, because if the conditions that are essential for good health are maintained, then the chances of getting a disease will be minimized. But at the same time, we can say that they are different because being health or good health means physical, mental and social well-being while being disease-free means not suffering from a particular disease.

Why do we Fall Ill Intext Questions Page No. 180

Question 1.
List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?
Answer:
Common symptoms which indicate sickness are:

1. Headache
2. Cough
3. Dysentery

If only one of these symptoms is present, we usually do not visit a doctor. This is because such symptoms do not have much effect on our general health and ability to work. However, if a person is experiencing these symptoms for quite sometime, then he needs to visit a doctor for proper treatment.

Question 2.
In which of the following case do you think the long – term effects on your health are likely to be most unpleasant?

1. If you get jaundice
2. If you get lice
3. If you get acne.
   Why?

Answer:
Jaundice is a disease that can cause long – term effects on our health. It is a chronic disease that lasts for a long period of time. Jaundice does not spread rapidly, but it develops slowly over a period of time.

Why do we Fall Ill Intext Questions Page No. 187

Question 1.
Why are we normally advised to take bland and nourishing food when we are sick?
Answer:
When we are sick, the normal body functions get disturbed. In such a situation, food that is easily digestible and contains adequate nutrients are required for the speedy recovery. Thus, bland and nourishing food is given during sickness.

Question 2.
What are the different means by which infectious diseases spread?
Answer:
The different modes of transmission of infectious diseases are:

1. Through Air: Certain disease – causing micro – organisms are expelled in air by coughing, sneezing, talking etc. These micro-organisms can travel through dust particles or water droplets in air to reach other people. For example, tuberculosis, pneumonia etc. spread through air.
2. Through Water: Sometimes causal micro – organisms get mixed with drinking water and spread water borne diseases. Cholera, for example is a water borne disease.
3. Through Sexual Contact: Sexual act between two people can lead to the transfer of diseases such as syphilis, gonorrhoea, AIDS etc.
4. Through Vectors: Certain diseases spread by animals called vectors. For example, mosquitoes spread malaria.

Question 3.
What precautions can you take in your school to reduce the incidence of infectious diseases?
Answer:
Precautions to reduce incidence of infectious diseases are:

1. Staying away from the infected person.
2. Covering mouth or nose while coughing or sneezing to prevent the spread of disease.
3. Drinking safe water.
4. Keeping the school environment clean to prevent multiplication vectors.

Question 4.
What is immunisation?
Answer:
Immunisation is defined as protection of the body from communicable diseases by administration of some agent that mimics the pathogen.

Question 5.
What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?
Answer:
The immunisation programmes available at the nearest health centre are DPT (Diphtheria, Pertusis, and Tetanus), polio vaccine, hepatitis B, MMR (Measles, Mumps, and Rubella), jaundice, typhoid etc. Of all these diseases, jaundice and typhoid are major health problems.

Why do we Fall Ill NCERT Textbook Exercises

Question 1.
How many times did you fall ill in the last one year? What were the illnesses?

1. Think of one change you could make in your habits in order to avoid any of/most of the above illnesses.
2. Think of one change you would wish for in your surroundings in order to avoid any of / most of the above illnesses.

Answer:
The illness was 2 – 3 times common – cold, occurred in a year:

1. One change I would make in my habits in order to avoid the above illness is that I would take proper diet rich in vitamin C and would avoid too cold food.
2. The surroundings should be neat and clean.

Question 2.
A doctor / nurse / health – worker is exposed to more sick people than others in the community. Find out how she / he avoids getting sick herself / himself.
Answer:
The following precautions must be taken by a doctor / nurse / health – worker:

1. Wearing a mask when in contact with a diseased person.
2. Keeping yourself covered while moving around an infected place.
3. Drinking safe water.
4. Eating healthy and nutritious food.
5. Ensuring proper cleanliness and personal hygiene.

Question 3.
Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Answer:
Common diseases are dysentry, malaria, viral fever / jaundice. Preventive Measures:

1. Cleanliness of surrounding neighbourhood i.e, removal of garbage from the streets / house and storage in a covered place till it is disposed off. Proper cleaning of drains and proper disposal of sewer water.
2. Removal of breeding places of mosquitoes like ditches with stagnant water.
3. Ensure supply of safe drinking water.

Or
Periodical programmes to educate people about prevention of disease.

Question 4.
A baby is not able to tell her / his caretakers that she / he is sick. What would help us to find out

1. that the baby is sick?
2. what is the sickness?

Answer:

1. The baby is sick can be determined by his / her behavioural changes such as constant crying of baby, improper intake of food, frequent mood changes etc.
2. The sickness is determined by symptoms or indications that can be seen in the baby. The symptoms include vomiting, fever, loose motion, paleness in the body etc.

Question 5.
Under which of the following conditions is a person most likely to fall sick?
(a) when she is recovering from malaria.
(b) when she has recovered from malaria and is taking care of someone suffering from chicken – pox.
(c) when she is on a four – day fast after recovering from malaria and is taking care of someone suffering from chicken – pox. Why?
Answer:
(c) A person is more likely to fall sick when she is on a four day fast after recovering from malaria and is taking care of someone who is suffering from chicken pox. This is because she is fasting during recovery and her immune system is so weak that it is not able to protect its own body from any foreign infection. If she is taking care of someone suffering from chicken pox, then she has more chances of getting infected from chicken pox virus and will get sick again with this disease.

Question 6.
Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles. Why?
Answer:
(c) You are more likely to fall sick when your friend is suffering from measles. This is because measles is highly contagious and can easily spread through respiration i. e., through air. Thus, if your friend is suffering from measles, stay away from him otherwise you might easily get infected with the disease.

Why do we Fall Ill Additional Questions

Why do we Fall Ill Multiple Choice Questions

Question 1.
Community health is related to:
(a) Social health
(b) Physical health
(c) Mental health
(d) All.
Answer:
(d) All.

Question 2.
Every disease have particular:
(a) Body weight
(b) temperature
(c) Sign
(d) Appearance change.
Answer:
(c) Sign

Question 3.
Condition for good community health is by maintaining:
(a) Cleanliness
(b) Pollution less atmosphere
(c) Economic growth
(d) All.
Answer:
(d) All.

Question 4.
Malaria is caused by:
(a) Vibrio cholerae
(b) Plasmodium vivax
(c) Andies
(d) H. pylori.
Answer:
(b) Plasmodium vivax

Question 5.
Vibrio cholerae is a:
(a) Agent
(b) Host
(c) Vector
(d) None.
Answer:
(a) Agent

Question 6.
Which one of the following is water born infectious disease?
(a) Common cold
(b) Peptic ulcers
(c) Cholera
(d) AIDS.
Answer:
(c) Cholera

Question 7.
Which one among the following is a viral disease?
(a) AIDS
(b) Cholera
(c) TB
(d) Typhoid.
Answer:
(a) AIDS

Question 8.
Which one among the following is a chronic disease?
(a) Cold
(b) Malaria
(c) Elephantiasis
(d) None.
Answer:
(c) Elephantiasis

Question 9.
In malaria disease, which one of the following is vector?
(a) Plasmodium vivax
(b) Mosquito
(c) Human
(d) Dog.
Answer:
(b) Mosquito

Question 10.
Which one of the following is mechanical cause of disease?
(a) Injury
(b) Microbes
(c) Heat
(d) All.
Answer:
(a) Injury

Question 11.
HIV – AIDS is transmitted by:
(a) Microbes
(b) Sexual contact
(c) Water
(d) All.
Answer:
(b) Sexual contact

Question 12.
Main factors which can help in public health hygiene:
(a) Availability of safe drinking water.
(b) Availability of clean environment.
(c) Spacious condition for living.
(d) All.
Answer:
(d) All.

Question 13.
Penicillin is a / an:
(a) Antigen
(b) Antibody
(c) Pathogen
(d) Host.
Answer:
(a) Antigen

Why do we Fall Ill Very Short Answer Type Questions

Question 1.
Write symptoms of a disease.
Answer:
Discomfort pain and tiredness is symptoms of a disease.

Question 2.
Is mental discomfort a disease?
Answer:
Yes.

Question 3.
When a part of body is hurt, can it affect all body? Why?
Answer:
Yes, because all body parts are connected internally.

Question 4.
Write name of two diseases caused by virus.
Answer:
AIDS, common cold.

Question 5.
Write name of two diseases caused by worms.
Answer:
Elephantiasis, intestine infection.

Question 6.
Write name of two deficiency diseases.
Answer:
Beri – Beri, Rickets.

Question 7.
What is a vector?
Answer:
Organism which transfer a disease is called a vector.

Question 8.
What is a host?
Answer:
Organism which bear disease and their causative agents is called host.

Question 9.
Name one genetical disorder.
Answer:
Haemophilia.

Question 10.
How malaria and dengue are spread?
Answer:
By species of mosquito.

Question 11.
Name two communicable diseases.
Answer:

1. AIDS
2. cold.

Question 12.
What become vector for a communicable disease?
Answer:
Host itself.

Question 13.
What kind of disease is AIDS?
Answer:
AIDS is a fatal viral disease.

Question 14.
Name two air born diseases.
Answer:

1. Influenza
2. pneumonia.

Question 15.
Name a disease against which vaccines are available.
Answer:
Typhoid.

Why do we Fall Ill Short Answer Type Questions

Question 1.
Define congenital diseases. Give some examples of such disease.
Answer:
Diseases or abnormalities present since birth are called congenital diseases. It is due to gene mutations (genetic factor) or environmental factors.
Examples:

• Colour blindness
• Cleft lip or palate.

Question 2.
Name the agent and vector which cause rabies.
Answer:
The causative agent of rabies is rabies virus (RV). The animals included humans can be infected and all of them can spread the disease.
Causes:

• Dogs
• rats
• cats
• monkeys
• squirrels
• cattle
• wolves
• racoons
• bears etc. can spread this disease.

Question 3.
What are acquired diseases?
Answer:
The diseases which develop after birth are called acquired diseases. It is categorized into

• Communicable Diseases(Infectious Diseases): malaria, influenza etc. and
• Non – Communicable Diseases: diabetes, scurvy, high blood pressure.

Question 4.
Write some common signs and symptoms of a disease if a brain is affected.
Answer:
Headache, fits, vomitting, unconsciousness etc.

Question 5.
What are infectious agents?
Answer:
The microorganisms which spread the disease from one person to other are called infectious agents.

Question 6.
Define ‘germ theory of disease’?
Answer:
Louis Pasteur proposed ‘germ theory of disease’ also called pathogenic theory of medicine. He stated that micro – organisms are the causes of many diseases.

Question 7.
What happen when kidneys of a person do not filter urine properly?
Answer:
If the kidneys of a person do not filter urine properly then the toxic substances which disturbs metabolism could be fatal.

Question 8.
Is skin, hairs, saliva form the first line of defence against diseases? If yes, then how?
Answer:
Yes, skin, nose hairs, saliva act as the first line of defence.

• Skin: It prevents the entry of microbes.
• Hairs: These prevent the entry of dust particles and germs.
• Saliva: It washes away bacterial growth from teeth and mouth.

Question 9.
What is immunity?
Answer:
Immunity refers to ability of the body to be resistant towards injury, poison or harmful pathogens. It is part of the defence reaction in the body. There are two types of immunity – natural or innate immunity and acquired or specific immunity.

Question 10.
Why are kids and elderly people more vulnerable to cold / flu?
Answer:
Kids are more vulnerable to cold and flu because their immune systems haven’t fully developed. Elderly people also more prone to catch a cold because of their poor health.

Question 11.
Define antibiotic. Explain how it is able to control bacterial infections but not viral infections.
Answer:
Antibiotics (anti means against and biotic means living) are types of medications which slows and destroy the growth of bacteria. They commonly block biochemical pathways important for bacteria. Many bacteria, for example, make a cell – wall to protect themselves. The antibiotic penicillin blocks the bacterial processes that build the cell wall. Thus, bacteria fail to build their cell – wall, stop multiplying and die out.

Question 12.
Name infectious diseases that are spread through air.
Answer:
Infectious diseases that spread through air are – sneezing, coughing, open pneumonia, tuberculosis, measles, SARS, chicken – pox.

Question 13.
How infectious diseases are spread through water? Give two examples.
Answer:
Open defecation, consuming contaminated water, inadequate hand washing causes infectious diseases through water. Water – borne diseases are cholera, typhoid etc.

Question 14.
Give few examples of direct and indirect contact diseases.
Answer:

1. Direct Contact Diseases: Examples of diseases spread by direct contact are common cold, tuberculosis, chicken pox, warts etc. Sexual Transmitted Diseases (STD) are Syphilis, AIDS, gonorrhoea.
2. Indirect Contact Diseases: Examples of diseases spread by indirect contact are Flu, TB, Chickenpox, urinal infections etc.

Why do we Fall Ill Long Answer Type Questions

Question 1.
Becoming exposed to or infected with an infectious microbe does not necessarily mean developing noticeable disease. Explain.
Answer:
Infected with a microbe does not mean developing a disease because an infectious microbe is able to cause a disease only. If the immune system of the person is weak but a person with strong immune system normally fights off microbes. We have cells which are specialised to kill the pathogenic microbes. These cells are active when infecting microbes enter the body and if they are successful in removing the pathogen, we remain disease – free. So, even if we are exposed to infectious microbes, the person will not catch the disease.

Question 2.
Give any four factors necessary for a healthy person.
Answer:
Factors necessary for a healthy person are as follows:

1. A clean environment with proper public health services.
2. Personal hygiene prevents infectious diseases.
3. A proper balanced diet and sufficient nourishment are necessary for good immune system of our body.
4. Immunisation / vaccination against severe diseases.

Question 3.
Why is AIDS considered to be a ‘Syndrome’ and not a disease?
Answer:
AIDS is considered a syndrome and not a disease because AIDS causing virus – HIV comes into the body via the sexual organs or any other means like blood transfusion and spread to lymph nodes all over the body. The virus damages the immune system of the body and the body can no longer fight off many minor infectious. Instead, every small cold can become pneumonia, or minor get infection can become severe diarrhoea. The effect of disease becomes very severe and complex, at times killing the person suffering from AIDS. Hence, there is no specific disease symptoms for AIDS but it results in a complex disease and symptoms.

Question 4.
(a) The signs and symptoms of a disease depend upon the tissues or organ the microbe targets. Explain giving any two examples.
(b) How does the immune system work against microbes?
(c) Name two diseases against which vaccines are available.
Answer:
(a) Disease – causing microbes enter the body through different means. These disease – causing micro – organisms are tissues specific or we can say that they target a specific organ.  If these microbes enter the body via the nose, the lungs are target and the symptoms are:

1. cough
2. breathlessness.

This is seen in the bacteria causing tuberculosis. If brain is targetted by these microbes, the symptoms will be headache, vomitting, fits or unconsciousness. This is seen in the bacteria causing meningitis.

(b) Immunisation is most important and effective way to raise resistance against the disease. Immunity may be two types:

1. Active immunity
2. Passive Immunity (artificial).

In active immunity, the body responds against disease – causing microbes and produces antibodies. The antibodies attack organ and kill the disease – causing microbes. In passive immunity, prepared antibodies are used against disease – causing microbes.

(c) We have vaccine against polio and tuberculosis.

Why do we Fall Ill Higher Order Thinking Skills (HOTS)

Question 1.
Why we cannot destroy virus?
Answer:
Virus attacks our body and consume proteins and RNA only. They do not have any metabolic pathway while other pathogens have their metabolic pathways. Our medicines stops the metabolic activity of pathogens and hence they get destroyed, but it is not possible in case of virus.

Question 2.
How vaccine stops disease while it is, itself a low dose of similar causative agent?
Answer:
Our body has a very strong immune system and it develops antigen to subside the effect of any new high quantity antibody entering in the body. Presence of chemical in small harmless quantity initiate development of antigen in body and when actually agent enters in the body, antigen fights easily with it.

Why do we Fall Ill Value Based Questions

Question 1.
Anya got vaccination, she told her friend Sakshi. Sakshi got scared and doubted if it was safe as it contains weakened pathogens which cause diseases. Later, Anya explained her the concept of vaccination and immunity. Answer the following questions:

1. What did Anya explain Sakshi?
2. What values did Anya possess?

Answer:

1. Anya explained that vaccine or weakened pathogen are not harmful to the body. Rather, they boost the person immunity against the same pathogen when it is actually encountered by the body is attacked by it leading to its destruction.
2. Anya possess the values of helpfulness and intelligence. She is practical.

Question 2.
Akash found in a blood test that his brother was HIV positive. His brother, due to this was expelled from the job. Only after intervention of NGO, he got it back.

1. Which disease is his brother suffering from?
2. Write its modes of transmission.
3. Write your views about the NGO and the organization where his brother worked.

Answer:

1. AIDS (caused by HIV).
2. • Mother to child (during pregnancy).
   • Using infected syringes.
   • Blood transfusion.
   • Sexual contact with infected person.
3. NGO has taken correct step and has helped Akash in fighting for injustice. While, organisation was wrong in its step as it does not spread by touching or by working with the infected person.

MP Board Class 9th Science Solutions

MP Board Class 7th Science Solutions Chapter 4 Heat

Heat Intext Questions

Question 1.
Boojho says, My left hand tells me that the water in mug C is hot and the right hand tells me that the same water is cold. What should I conclude?
Answer:
Both of the conclusions are true relative to each hand. But a single conclusion can not be drawn from the given information.

Question 2.
Boojho wondered which of the two scales shown in fig. he should read. Paheli told him that India has adopted the Celsius scale and we should read that scale. The other scale with the range 94-108 degrees is the Fahrenheit scales (°F). It was in use earlier.

Answer:
Yes

Question 3.
Boojho got a naughty idea. He wanted to measure the temperture of hot milk using a clinical thermometer. Paheli stopped him from doing so?
Answer:
Yes, do not use a clinical thermometer for measuring the temperature of any object other than he human body because it may break.

Question 4.
Boojho now understand why clinical thermometer can not be used to measure high temperatures. But still wonders whether a laboratory thermometer can be used to measure his body temperature?
Answer:
Yes, laboratory thermometer can also be used for measuring body temperature.

Question 5.
Boojho wonders why the level of mercury should change at all when the bulb of the thermometer is brought in contact with another object?
Answer:
The temperature of other object may not be the same as that of the bulb of the thermometer. When bulb is brought in contact with that object, the temperature of the bulb changes. Thus, the level of mercury also changes.

Question 6.
Paheli asks: “Does it mean that heat will not be transferred if the temperature of two objects is the same?”
Answer:
Yes.

Activities
Activity 1
Lost some objects you use commonly in given table. Mark these objects as cold or hot?
Answer:

Activity 2
Measure the body temperature of some of your friends (at least 10) with a clinical thermometer.
Answer:
Observation for body temperature of some persons.

Activity 3
Take a rod or flat strip of a metal, say of aluminium or iron. Fix a few small wax pieces on the rod. These pieces should be at nearly equal distances (fig.). Clamp the rod to a stand. If you do not find a stand, you can put one end of the rod in between bricks. Now, heat the other end of the rod and observe.

What happens to the wax pieces? Do these pieces begin to fall? Which piece fall the first? Do you think that heat is transferred from the end nearest to the flame to the other end?
Answer:
The wax pieces start to melt and fall down.
Yes.
The piece nearest to the flame tall first. Yes, heat is transferred from the end nearest to the flame to the other end.

Activity 4
Heat water in a small pan or a beaker. Collect some articles such as a steel spoon, plastic scale, pencil and divider. Dip one end of each of these articles in hot water (fig.). Wait for a few minutes. Touch the other end. Enter your observation in Table.

Activity 5
Explain with activity heat transfer by conduction method?
Answer:
1. Aim:
To understand, ‘heat transfer by conduction’.

2. Required material:
Iron stick, some nails, candle.

3. Process:
Attach the nails on thin iron rod at some intervals with help of candle-wax as shown in figure. Now heat one end of iron rod with candle.

4. Analysis:
When we Start heating one end of iron rod, nails start falling one by one. The nail which is adjacent to hot end of iron – rod, falls first and then other nails 1 fall in sequence. Falling of nails in sequence indicate heat flow by conduction. Some time later, heat reaches to other end of rod and entire rod becomes hot.

5. Conclusion:
Heat transfer in iron – rod takes place by conduction.

Activity 6
Take a round bottom flask (if flask is not available, a beaker can be used). Fill it two – thirds with water. Place it on a tripod, or make some arrangement to place the flask in such a way that you can heat it by placing a candle below it. Wait till the water in the flask in still. Place a crystal of potassium permanganate at the bottom of the flask gently using a straw. Now, heat the water by placing the candle just below the crystal. Write your observation in your notebook and also draw a picture of what you observe.
Answer:
When water is heated, the water near the flame gets hot. Hot water rises up. The cold water from the sides moves

down towards the source of heat. This water also gets hot and rises and water from the sides moves down. This process continues till the whole water gets heated. This mode of heat transfer is knwon as convection.

Heat Text book exercises

Question 1.
State similarities and differences between the laboratory thermometer and the clinical thermometer?
Answer:
Similarities:

1. Both use mercury.
2. Both measure temperature.

Differences:
1. The range of a mercury thermometer is 100°C. A mercury thermometer having graduations from 0°C to 100°C while the temperature interval marked on the clinical thermometers ranges from 35°C to 43°C.

2. The temperature on laboratory thermometer falls by itself, but not so in clinical thermometer. In clinical thermometers, a jerk is given so that it is set again for measuring human body temperature.

Question 2.
Give two emamples each of conductors and insulators of heat?
Answer:
Conductors: Copper, Aluminium

Insulators: Wood, Plastic

Question 3.
Fill in the blanks:

1. The hotness of an object is determined by its ………………
2. Temperature of boiling water cannot be measured by a ………………. thermometer.
3. Temperature is measured in degree …………………
4. No medium is required for tansfer of heat by the process of ………………..
5. A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of …………………..
6. Clothes of ………………. dolours absorb heat better than clothes of light colours.

Answer:

1. Temperature
2. Clinical
3. Celsius
4. Radiation
5. Conduction
6. Dark/black.

Question 4.
Match the following:

Answer:

(i) (d)
(ii) (c)
(iii) (b)
(iv) (a)

Question 5.
Discusss why wearing more layers of clothing during winter keeps us warmer than waering just one thick piece of clothing?
Answer:
More layers of clothing keep us warm in winters as they have a lot of space between them. Air is a poor conductor of heat. This increases the insulation and thus, comfortability warm of the clothes as a whole.

Question 6.
Look at fig Mark where the heat is being transferred by conduction, by convection and by radiation?
Answer:

Question 7.
In places of hot climate it is advised that the outer walls of houses be painted white. Explain?
Answer:
In places of hot climate it is advised that the outer wall of houses be painted white because white colour do not radiate heat easily.

Question 8.
One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be

1. 80°C
2. More than 50°C but less than 80°C
3. 20°C
4. Between 30°C and 50°C

Answer:
4. Between 30°C and 50°C.

Question 9.
An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will

1. Flows from iron ball to water.
2. Not flow from iron ball to water or from water to iron ball.
3. Flows from water to iron ball.
4. Increase the temperature of both.

Answer:
2. Not flow from iron ball to water or from water to iron ball.

Question 10.
A wooden spoon is dipped in a cup of ice cream. Its other end

1. Becomes cold by the process of conduction.
2. Becomes cold by the process of convection.
3. Becomes cold by the process of radiation.
4. Does not become cold.

Answer:
4. Does not become cold.

Question 11.
Stainless steel pans are usually provided with copper bottoms. The reason for this could be that

1. Copper bottom makes the pan more durable
2. Such pans appear colourful
3. Copper is a better conductor of heat than the stainless steel
4. Copper is easier to clean than the stainless steel.

Answer:
3. Copper is a better conductor of heat than the stainless steel

Extended Learning – Activities and Projects

Question 1.
Go to a doctor or your nearest health centre. Observe the doctor taking temperature of patients Enquire?

1. Why she dips the thermometer in a liquid before use.
2. Why the thermomter is kept under the tongue.
3. Whether the body temperature can be measured by keeping the thermomter at some place other than the mouth.
4. Whether the temperature of different parts of the body is the same or different. You can add more questions which come to your mind.

Answer:

1. Because to prevent infection. This liquid is an antiseptic.
2. Because the temperature below the tongue represents actual temperature of body.
3. Yes, but not so desirable.
4. Temperature of different parts of the body are different.

Question 2.
Go to a veterinary doctor (a doctor who treats animals)?
Discuss and find out the normal temperature of domesitc animals and birds.
Answer:

Question 3.
Wrap a thin paper strip tightly around an iron rod. Try to burn the paper with candle while rotating the iron rod continuously. Does it burn? Explain your observation?
Answer:
No, the paper strip does not burn. Iron it a good conductor of heat. It takes away .the heat from paper and saves it from burning.

Question 4.
Take a sheet of paper. Draw a spiral on it as shown in the fig. Cut out the paper along the line. Suspend the paper as shown in figure, above a lighted candle. Observe what happens. Think of an explanation?

Answer:
The paper spiral keeps moving. This is so because the air above the flame moves up due to convection.

Question 5.
Take two similar transparent glass bottles having wide mouths. Put a few crystals of potassium permanganate or pour a few drops of ink in one bottle. Fill this bottle with hot water. Fill the other bottle with cold water. Cover the cold water bottle with a thick piece of paper such as a postcard. Press the postcard firmly with one hand and hold the bottle with the other hand. Invert the bottle and place it on top of the hot water bottle. Hold both the bottles firmly. Ask some other person to pull the postcard. Observe what happens. Explain.
Answer:
Do with the help of your subject teacher.

Heat Additional Important Questions

Objective Type Questions

Question 1.
Choose the correct alternative:

Question (i)
By which method heat transfer takes place in solids –
(a) Convection
(b) Conduction
(c) Radiation
(d) All three.
Answer:
(b) Conduction

Question (ii)
When can feel the hotness of some hot substance like electric iron from a little distance by which method?
(a) Convection
(b) Conduction
(c) Radiation
(d) All three methods.
Answer:
(c) Radiation

Question (iii)
By which method sun’s heat reaches to earth –
(a) Conduction
(b) Convection
(c) Radiation
(d) Conduction and convection.
Answer:
(c) Radiation

Question (iv)
The handle of cooker is make up of bakelite because it is –
(a) Cheap
(b) Looks beautiful
(c) Bad conductor of heat
(d) Good conductor of heat.
Answer:
(c) Bad conductor of heat

Question (v)
By which of the following processes the water circulates in radiator of the bus engine and keeps the engine cool –
(a) Convection
(b) Radiation
(c) Conduction
(b) Conduction and radiation.
Answer:
(a) Convection

Question (vi)
Ice is kept in four boxes made of the following materials. If the same quantity of ice is kept for same time in the boxes, in which box the ice will melt least –
(a) Lead
(b) Wood
(c) Steel
(d) Thermocoal.
Answer:
(d) Thermocoal.

Question (vii)
In radiation, heat energy travel in –
(a) Curred lines
(b) Zig – zag lines
(c) Straight lines
(d) None of these.
Answer:
(c) Straight lines

Question (viii)
A thermos flask prevents loss or gain of heat by –
(a) Radiation only
(b) Conduction only
(c) Convection only
(d) None of these.
Answer:
(b) Conduction only

Question 2.
Fill in the blanks:

1. The measure of …………… energy is temperature.
2. ……………. is the apparatus to measure temperature.
3. The temperature at which a substance changes its state from solid to liquid is called its …………….
4. In convection, water travels from …………. region to the ……………. region.
5. The black bodies are good ………….. of heat.
6. Water is a …………… conductor of heat.
7. Transfer of energy between different part of a body is called ……………
8. Shining bodies are poor ……………. of heat energy.
9. Dark objects absorbs …………… heat then light coloured object.

Answer:

1. Heat
2. Thermometer
3. Melting point
4. Hotter, colder
5. Absorber
6. Bad
7. Conduction
8. Radiators
9. More.

Which of the following statements are True (T) or False(F):

1. Heat is a form of energy.
2. Heat flows from a lower temperature to a higher temperature.
3. The temperature of a healthy adult is 98.4°C.
4. Iron is better conductor of heat than aluminium.
5. The temperature at which a substance changes its state from solid to liquid is called its melting point.
6. In thermometer highest points is 100°C.
7. In thermometer’s the lowest point is 273°K Radiation of heat can take place without a medium. See
8. breeze is the blowing of air from sea toward the land.
9. Air is a good conductor of heat.

Answer:

1. Ture (T)
2. False (F)
3. False (F)
4. False (F)
5. True (T)
6. Ture (T)
7. True (T)
8. True (T)
9. True (T)
10. False (F).

Question 4.
Match the items in Column A with Column B:

Answer:

(i) (d)
(ii) (a)
(iii) (b)
(iv) (c)

Heat Very Short Answer Type Questions

Question 1.
Define clinical thermometer?
Answer:
The thermometer that is used to measures our body temperature is called a clinical thermometer.

Question 2.
What is the range of a clinical thermometer?
Answer:
35°C to 42°C.

Question 3.
Why is range of a clinical thermometer is chosen to be 35°C to 42°C?
Answer:
The clinical thermometer is designed to measure the temperature of human body only. The temperature of human body normally does not go below 35°C or above 42°C. That is the reason why this thermometer has the range 35°C to 42°C.

Question 4.
What is the use of kink in thermometer?
Answer:
Kink prevents mercury level from falling on its own.

Question 5.
Why dose the mercury not fall or rise in a clinical thermometer when taken out of the month?
Answer:
The kink prevents the mercury level from falling down.

Question 6.
Name two substances which contract on heating.
Answer:
Bismuth, Ice.

Question 7.
Which substances has the highest heat capacity?
Answer:
Water.

Question 8.
Which gets hotter soon, land or water?
Answer:
Land.

Question 9.
What is thermos flask?
Answer:
Thermos flask is a device in which heat losses due to conduction, convention and radiation are minimised.

Question 10.
How does the heat travel in air? In which direction does the smoke go?
Answer:
Heat moves in air by convection. The smoke moves in the upward direction.

Question 11.
How does the heat from the sun reaches?
Answer:
By radiation.

Question 12.
Why are you advised to use an umbrella when you go out in the Sun?
Answer:
The umbrella protects us from heat rays of the Sun.

Question 13.
What is temperature?
Answer:
Temperature of an object is the degree of its hotnees. It tells us how hot or cold the object is.

Question 14.
Name the instrument we use to measure temperature.
Answer:
We use thermometers to measure the temperature.

Question 15.
Write the S.I. unit of heat?
Answer:
Joule.

Question 16.
Write the names of the methods of heat transfer?
Answer:
The names of methods of heat transfer are conduction, convection and radiation.

Question 17.
The iron nails from aluminium rods falls faster than from iron rod. What do you conclude from this statement?
Answer:
It means that aluminium is a better conductor of heat as compared to iron. So it passes heat much quickly to the iron nails and they fall down due to melting of wax.

Question 18.
Why in summer days does the fan give hot air first in a closed room when it is switched on?
Answer:
In a closed room the hot air remains at top because it is lighter. So when fan is turned on, it circulates the upper air first and it gives a current of hot air.

Question 19.
Why are the cooking utensile made up of metals?
Answer:
Cooking utensils are made up of metals as they are good conductor of heat. They transfer the heat to the food inside quickly and the food is cooked easily.

Question 20.
What are good conductors of heat? Give examples.
Answer:
Substances which allow the heat to pass through them are called good conductors of heat. Examples : all metal like iron, aluminium, copper and alloys like steel etc.

Question 21.
What are bad conductor of heat? Give examples.
Answer:
Substance which do not allow the heat to pass through them are called bad conductor of heat.
Examples: wood, paper, asbestos, rubber etc.

Question 22.
Why do fire workers wear bright clothes?
Answer:
Fire worker wears bright clothes because bright clothes are good reflector of heat. They send back the heat falling on them. Thus fire workers do not catch fire and heat easily.

Question 23.
On a cold winter night, why do we feel colder when the sky clear than when it is cloudy?
Answer:
As clouds are bad conductor of heat, they do not allow the warm air around us to flow up. So heat remains near the ground and we feel warmer.

Question 24.
When does the conduction of heat stop in two bodies in contact?
Answer:
The conduction of heat stops in two bodies in contact when the two bodies attain equal temperature. That is the two bodies have no temperature difference.

Question 25.
How do you note the temperature of the body with thermometer?
Answer:
When bulb of thermometer comes in contact with our body. The mercury in the thin tube rises up. When the temperature of thermometer and body becomes equal, the level of the mercury does not rise further. This is the temperature of the body.

Heat Short Answer Type Questions

Question 1.
What is the difference between heat and temperature?
Answer:
Heat:

1. Heat is a form of energy. It flows from a body at higher temperature to a body at lower temperature.
2. Heat is measured in Joules or Calorie.

Temperature:

1. Temperature is a measure of energy in the form of heat. Generally the temperature of a body increases when it is heated.
2. Temperature is measured in Celcius.

Question 2.
On basis of what properties, mercury is used in thermometer?
Answer:
Mercury is used in thermometer because of the following properties:

1. Thermal expansion is uniform in mercury.
2. As it is shining silvery white, its thermal expansion is seen easily. This helps in noting the reading of thermometer easily.
3. It does not stick to the surface of glass.
4. Mercury does not freeze at 0°C because it’s freezing point is 39°C.

It does not boil at 100°C because it’s boiling point is 357°C. Hence, mercury has wide range of temperature between its freezing point and boiling point.

Question 3.
Distinguish between conduction and convection.
Conduction:

1. In conduction the molecules do not leave their position.
2. It generally takes place in solid.

Convection:

1. In convection the molecules of the substance actually move from hotter region to colder region.
2. It generally takes place in gases and liquids.

Question 4.
Why should we wear dark coloured clothes in winter and light coloured clothes in summer?
Answer:
Bright clothes objects tend to reflect back the heat more, than to absorb the heat. Therefore, it is advisable to wear them in summer. On the other hand, dark coloured clothes have a greater tendency to absored and hence “retain” the heat. Hence they are worn in winter.

Question 5.
Why rise in temperature in two substances of equal quantity is not same even through equal amount of heat is given to them?
Answer:
The same quantity of heat supplied to the same amount of different substances, then the rise in teperature would not be same bacause the rise in temperature of the substance would depend on their specific heat. The temperaute of the substance which has less specific heat would rise more.

Question 6.
What are the precautions to be observed while reading a clinical thermometer?
Answer:
Precautions to be observed while reading a clinical thermometer are:

1. Thermometer should be washed before and after use, preferably with an antiseptic solution.
2. Ensure that before use, the mercury level is below 35°C.
3. Read the thermometer keeping the level of mercury along the line of sight.
4. Handle the thermometer with care. If it hits against some hard object, it can break.
5. Don’t hold the thermometer by the bulb while reading it.

Question 7.
What are the precautions to be observed while reading a laboratory thermometers?
Answer:
In addition to the precautions needed while reading a clinical thermometer, the laboratory thermometer

1. Should be kept upright not tilted.
2. Bulb should be surrounded from all sides by the substance of which the temperature is to be measured. The bulb should not touch the surface of the container.

Question 8.
Define mamixum – minimum thermometer.
Answer:
Different types of thermoters are used for different puroposes. The maximum and minimum temperatures of the previous day, reported in weather reports, are measured by a thermometer called the maximum – minimum thermometer.

Question 9.
Draw diagram of the laboratory thermometer. Mark the lower and upper fixed temperatures on a Celsius scale and indicate the values in Kelvin scale aslo.
Answer:

Question 10
Name three different types of thermometers. Which of these is most sensitive?
Answer:
The three different types of thermometers are:

1. Mercury thermometer
2. Alcohol thermometer
3. Gases thermometer.

Mercury thermometer is used to measure nominal temperature. Alcohol thermometer is used to measure very low temperature. The gaseous thermometer is the most sensitive of all, as the gases are very sensitive to the slightest temperature change. The gaseous thermometers are rarely used because of the difficulty they pose in handling.

Question 11.
Define digital thermometers with diagram?
Answer:
There is a lot of concern over the use of mercury in thermometers. Mercury is a toxic substance and is very difficult to dispose of if a thermometer breaks. These days, digital thermometers are available which do not use mercury.

Heat Long Answer Type Questions

Question 1.
Explain with experiment the method of heat transfer by radiation?
Answer:
To know that the amount of heat absorbed or radiated by a substance depends upon colour of a substance.

Required Material:
Two containers of same metal, two thermometer, black and white colour, two cardboard pieces.

Procedure:

1. Colour the outer surface of one container with black and other with white.

2. Add equal quantity of tap water in both and insert thermometer by making a hole at the centre of card board as shown in picture.

3. Keep both containers for about 30 minutes under the sun. Then note down the temperature of both the containers.

4. Now add same quantity of hot water heated upto 50 to 60°C in both containers. Arrange the card board and thermometer properly and keep both of them is shadow for about 10 minutes. Then note down temperature of water from both containers.

Analysis:

Position 1.
After keeping containers for 30 minutes under the sun, you will see that, there is more increase in temperature of water in black container in comparision with white one. It is because black or dark colours are good absorbers of heat while white (light) colour is not.

Position 2.
After keeping the containers for 10 minutes in shadow, you will see that water in black container has cooled more than the water in white container. It is because black or dark colours are good emitters of heat, while white (light) colours are not.

Conclusion:

1. Black or dark colour are good absorbers or emitters of heat.
2. White or light colurs are good reflectors of heat. It means they are not good absorbers or emitters of heat.
3. The amount of heat emitted or absorbed by a substance depends upon colour of a substance.

Question 2.
Write some facts which indicates that sun light reaches to us by method of radiation?
Answer:
Medium is required for transfer of heat by conduction and convection process. When you stand under the sun, you experience heat. Heat reaches upto us from the sun. It is necessary to know following facts:

1. Air is poor conductor of heat hence heat is not transfered by conduction method in air.

2. Sun’s heat does not reach upto us by convection process also. Beacuse, you know that, convection will start only after earth is heated.

3. There is vacuum between sun and errth i.e. there is no medium. Hence sun’s heat can not reach upto us by conduction or convection method because medium is required for both methods. It means that sun’s heat reached us by some other method called radiation.

Question 3.
How does the highest and lowest constant point of thermometer marked?
Answer:
Two constant points i.e., lowest and highest are required to be marked while graduating the thermometer.

The lowest constant point:
The thermometer bulb is kept in a melting ice as shown in figure. Mercury descends in tube and remains constant after some time. This point is marked. This is lowest constant point of thermometer.

Highest constant point:
The thermometer bulb is kept in vapour of pure boiling water. Mercury ascends in tube and remains constant after some time. This point is marked. This is the highest constant point of thermometer.

Celcius scale:
Lowest constant point (temperature of melting ice) is indicated by °C and highest constant point (temperature of boiling water) is indicated by 100°C in this scale. The length between these two point is divided into 100 equal parts. The value of each parts is 1°C.

Question 4.
How does sea breeze flow?
Answer:
Convection current has got an important role in change of seasons. Sea breeze is the best example of this principle. In fact during day time, seashore land gets hotter earlier than water. Air in contact with it, becomes hot and rises. (Density of hot air is less and hence it is lighter) and hence to take its place cold air above sea flows towards seashore. Because of it, during day time sea breeze flows.

During night time, this process gets reversed. See water becomes cool later than seashore during night time. (As the specific heat capacity of water is more than the seashore land, it takes longer time to become hot and also takes longer time to become cool). Hence during night time, temperature of sea is more than seashore. As a result surface air of sea gets hotter and rises and air above seashore takes its place. In this way during night time cool air flows towards sea.

Question 5.
What is thermometer? Describe its construction?
Answer:
A thermometer is a device which is used to measure temperature accurately. The two commonly used thermometers are clinical thermometer and laboratory thermometer. The clinical thermometer is used by doctors to measure the body temperature. The laboratory thermometer is used in laboratories to measure melting point and boiling points.

A thermometer consists of a very fine capillary glass tube attached to a bulb containing mercury. In laboratory  thermometer the mercury is at zero mark when placed in ice and is at hundred mark when placed in boiling water. Therefore, zero, mark is considered as lower fixed point and 100 mark is considered as upper fixed point (see fig.).

Question 6.
Explain the structure or thermos flask with neat diagram?
Answer:
Thermos Flask was prepared first of all by Sir James Debar. It is used for storing cold or hot liquids for hours together. It is designed in such a way that heat transfer by conduction, convection and radiation should be minimum.

MP Board Class 7th Science Solutions

MP Board Class 9th Science Solutions Chapter 14 Natural Resources

Natural Resources Intext Questions

Natural Resources Intext Questions Page No. 193

Question 1.
How is our atmosphere different from the atmospheres on Venus and Mars?
Answer:
Earth’s atmosphere has mixture of nitrogen (79%), oxygen (20%), and a small fraction of carbon dioxide, water vapours and other gases which makes the existence of life possible on Earth while the atmospheres on Venus and Mars mainly has carbon dioxide. Approximately, 95% to 97% is carbon dioxide is present on these planets which do not support existence of life.

Question 2.
How does the atmosphere act as a blanket?
Answer:
Atmosphere is a mixture of various gases along with vapour and submerged particles. It surrounds the earth and separates it from outer space. As a blanket stop interaction between body covered inside and atmosphere outside, in similar way atmosphere stops interaction between earth and space.
The most important isolations done by atmosphere are:

1. It keeps the average temperature of the Earth fairly constant during day time and even during the course of whole year.
2. It prevents a sudden increase in the temperature during day time.
3. It slows down the escape of heat from the surface of the Earth into outer space during night time.

Question 3.
What causes winds?
Answer:
Atmospheric pressure and temperature difference generates wind. As earth surface is not similar everywhere even at some places it is occupied by huge water bodies, lava emitting volcanoes, moist forest etc., a difference in temperature and pressure arises and to maintain equilibrium wave of pressure moves which we feel or notice as wind.

Question 4.
How are clouds formed?
Answer:
During day time, a large amount of water evaporates from various water bodies and of earth surface and through biological activities such as transpiration and respiration and mix up into the air. This causes the air in the atmosphere to heat up and since air is a bad conductor of heat, when this heated air rises, it expands and cools, which results in the condensation and formation of water droplets. The presence of dust and other suspended particles in air also facilitates cloud formation. The gathering of water droplets leads to the formation of clouds.

Question 5.
List any three human activities that you think would lead to air pollution.
Answer:
Three human activities leading to air pollution are:

1. Smoke from industrial and manufacturing activities etc.
2. Burning of fossil fuels for household and commercial purpose.
3. Spreading farming chemicals such as crop dusting, insect / pest killers, fertilizer dust etc.

Natural Resources Intext Questions Page No. 194

Question 1.
Why do organisms need water?
Answer:
Water is the major component of living organism some of the living organism has up to 90% of water of their body weight. Water is a wonderful liquid, it helps in performing most of the functions of our body like digestion, cell sap and oilier content formation, transportation of substance from one place to another inside the body etc.

Question 2.
What is the major source of fresh water in the city’town/ village where you live?
Answer:
The major source of fresh water near me is river.

Question 3.
Do you know of any activity which may be polluting this water source?
Answer:
Dumps from industrial activities, household works for various purpose in the fresh water sources are main activities which causes pollution. Air pollution which generates acid rain and spread submerged dust is also responsible for polluting water resources.

Natural Resources Intext Questions Page No. 196

Question 1.
How is soil formed?
Answer:
The process of soil formation is termed ‘paedogenesis’. Soil is formed mainly by the weathering of rocks through various physical chemical and biological processes with the help of various factors such as the sun, water, wind, and living organisms. It is made up of mineral particles, organic materials, air, water and living organisms. During day time, the rocks are heated up by solar rays. This causes the rocks to expand. During night time, these rocks cool down and contracts. It causes weathering of rock and formation of soil.

1. Water: It helps in breaking of rocks in two ways:
   • It goes into the cracks and crevices formed in the rocks. When this water freezes, its volume increases. As a result, the size of the cracks also increases. This helps in the weathering of rocks.
   • Water moving at fast speed carries big and small particles of rock downstream. These rocks rub against each other, resulting in breaking down of rocks. These smaller particles are carried away by running water and deposited down its path.
2. Wind: Strong winds carry away rocks, which causes rubbing of rocks. This results in the breaking down of rocks into smaller and smaller particles.
3. Living Organism: Some living organisms like lichens help in the formation of soil. Lichens grow on rock surfaces and converts them into powdery form and make soil layer. In the same way, the plants like moss also helps in the making of fine soil particles.

Question 2.
What is soil erosion?
Answer:
The blowing away or washing away of land surface by wind or water is known as soil erosion.

Question 3.
What are the methods of preventing or reducing soil erosion?
Answer:
The methods of preventing or reducing soil erosion are:

1. Plantation of tress and plants.
2. Prevention of deforestation.
3. Prevent excessive grazing.

Natural Resources Intext Questions Page No. 201

Question 1.
What are the different states in which water is found during the water cycle?
Answer:
Water is found in three different states during the water cycle:

1. Solid (snow, ice).
2. Liquid water (ground water, river water, etc.)
3. Gaseous state (water vapours).

Question 2.
Name two biologically important compounds that contain both oxygen and nitrogen.
Answer:
Two biologically important compounds that contain both oxygen and nitrogen are:

1. Amino acids.
2. Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).

Question 3.
List any three human activities which would lead to an increase in the carbon dioxide content of air.
Answer:
Three Human activities are:

1. Burning of fuels in various processes like heating, cooking, transportation and industry.
2. Human induced forest fires.
3. The process of deforestation includes the cutting down of trees. This decreases the uptake of carbon dioxide for photosynthesis. Eventually, the content of carbon dioxide increases.

Question 4.
What is the greenhouse effect?
Answer:
Some gases like carbon dioxide, methane, nitrous oxide prevent the escape of heat from the Earth’s surface by trapping it. This increases the average temperature of the Earth. This is called the green house effect.

Question 5.
What are the two forms of oxygen found in the atmosphere?
Answer:
The two forms of oxygen found in the atmosphere are:

1. Diatomic molecular form with chemical formula O₂.
2. Triatomic molecular form with chemical formula O₃ known as ozone.

Natural Resources NCERT Textbook Exercise

Question 1.
Why is the atmosphere essential for life?
Answer:
The atmosphere is essential for life because it maintains an appropriate climate for the sustenance of life by carrying out the following activities:

1. Atmosphere keeps the average temperature of the earth fairly constant during day time.
2. It prevents a sudden increase in temperature during day time.
3. It also slows down the escape of heat from the surface of the earth into outer space during night time.

Question 2.
Why is water essential for life?
Answer:
Water is essential for life because of the following reasons:

1. Most biological reactions occur when substances are dissolved in water. Thus, all cellular processes need water as a medium to take place.
2. Transportation of biological substances needs water as a medium.

Question 3.
How are living organisms dependent on the soil?
Or
Are organisms that live in water totally independent of soil as a resource?
Answer:
Almost all living organisms are dependent on soil. Some depends directly, while some depends indirectly. Plants need soil for getting support as well as nutrients to prepare their food. On the other hand, organisms depend on plants for food and other substances that are essential for life. Herbivores depend directly upon plants and carnivores depend upon animals, which in turn depend upon plants for food. This makes them depend on soil indirectly.

Organisms that live in water are not totally independent of soil as a resource. These organisms depend on aquatic plants for food and other substances. These aquatic plants in turn require minerals for their sustenance. These minerals are carried to water bodies from soil by rivers, rain water etc. Without the supply of minerals from the soil to the water bodies, it is impossible to imagine aquatic life.

Question 4.
You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer:
The meteorological department of the government collects data on the elements of weather such as maximum and minimum temperatures, maximum and minimum humidity, rainfall, wind speed etc. They are able to study these elements using various instruments. The maximum and minimum temperature of a day is measured by a thermometer known as the maximum – minimum thermometer. Rain fall is measured by an instrument known as the rain gauge. Wind speed is measured by anemometers. There are various instruments used to measure humidity.

Question 5.
We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Answer:
Yes. Isolating human activities to specific areas would help in reducing levels of pollution. For example, setting up of industries in isolated regions will control pollution to some extent. The pollution caused by these industries will not contaminate water resources, agriculture land, fertile land, etc.

Question 6.
Write a note on how forests influence the quality of our air, soil and water resources.
Answer:
Forests influence the quality of our air, soil, and water resources in various ways. Some of them are:

1. Forests balance the percentages of carbon dioxide and oxygen in the atmosphere. The increasing amount of carbon dioxide caused by human activities is balanced by a larger intake of carbon dioxide by plants during
   the process of photosynthesis. Simultaneously, a large amount of oxygen is released.
2. Forests prevent soil erosion. Roots of plants bind the soil tightly in a way that the surface of the soil cannot be eroded away by wind, water etc.
3. Forests help in the replenishment of water resources. During the process of transpiration, a huge amount of water vapour goes into the air and condenses to form clouds. These clouds cause rainfall that recharge water bodies.

Natural Resources Additional Questions

Natural Resources Multiple Choice Questions

Question 1.
The atmosphere of the earth is heated by radiations which are mainly ___________ .
(a) radiated by the sun
(b) re – radiated by land
(c) re – radiated by water
(d) re – radiated by land and water.
Answer:
(d) re – radiated by land and water.

Question 2.
If there were no atmosphere around the earth, the temperature of the earth will ___________ .
(a) increase.
(b) go on decreasing.
(c) increase during day and decrease during night.
(d) be unaffected.
Answer:
(c) increase during day and decrease during night.

Question 3.
What would happen, if all the oxygen present in the environment is converted to ozone?
(a) We will be protected more.
(b) It will become poisonous and kill living forms.
(c) Ozone is not stable, hence it will be toxic.
(d) It will help harmful sun radiations to reach earth and damage many life forms.
Answer:
(b) It will become poisonous and kill living forms.

Question 4.
One of the following factors does not lead to soil formation in nature ___________ .
(a) the sun
(b) water
(c) wind
(d) polythene bags.
Answer:
(d) polythene bags.

Question 5.
The two forms of oxygen found in the atmosphere are ___________ .
(a) water and ozone
(b) water and oxygen
(c) ozone and oxygen
(d) water and carbon – dioxide.
Answer:
(c) ozone and oxygen

Question 6.
The process of nitrogen – fixation by bacteria does not take place in the presence of ___________ .
(a) molecular form of hydrogen
(b) elemental form of oxygen
(c) water
(d) elemental form of nitrogen.
Answer:
(b) elemental form of oxygen

Question 7.
Rainfall patterns depend on ___________ .
(a) the underground water table.
(b) the number of water bodies in an area.
(c) the density pattern of human population in an area.
(d) the prevailing season in an area.
Answer:
(b) the number of water bodies in an area.

Question 8.
Among the given options, which one is not correct for the use of large amount of fertilisers and pesticides?
(a) They are eco – friendly.
(,b) They turn the fields barren after sometime.
(c) They adversely affect the useful component from the soil.
(d) They destroy the soil fertility.
Answer:
(a) They are eco – friendly.

Question 9.
The nitrogen molecules present in air can be converted into nitrates and nitrites by ___________ .
(a) a biological process of nitrogen fixing bacteria present in soil.
(b) a biological process of carbon fixing factor present in soil.
(c) any of the industries manufacturing nitrogenous compounds.
(d) the plants used as cereal crops in field.
Answer:
(a) a biological process of nitrogen fixing bacteria present in soil.

Question 10.
One of the following processes is not a step involved in the water – cycle operating in nature ___________ .
(a) evaporation
(b) transpiration
(c) precipitation
(d) photosynthesis.
Answer:
(d) photosynthesis.

Question 11.
The term “water – pollution” can be defined in several ways. Which of the following statements does not give the correct definition?
(a) The addition of undesirable substances to water – bodies.
(b) The removal of desirable substances from water – bodies.
(c) A change in pressure of the water bodies.
(d) A change in temperature of the water bodies.
Answer:
(c) A change in pressure of the water bodies.

Question 12.
Which of the following is not a green house gas?
(a) Methane
(b) Carbon dioxide
(c) Carbon monoxide
(d) Ammonia.
Answer:
(d) Ammonia.

Question 13.
Which step is not involved in the carbon – cycle?
(a) Photosynthesis
(b) Transpiration
(c) Respiration
(d) Burning of fossil fuels.
Answer:
(b) Transpiration

Question 14.
‘Ozone – hole’ means
(a) a large sized hole in the ozone layer.
(b) thinning of the ozone layer.
(c) small holes scattered in the ozone layer.
(d) thickening of ozone in the ozone layer.
Answer:
(b) thinning of the ozone layer.

Question 15.
Ozone – layer is getting depleted because of ___________ .
(a) excessive use of automobiles.
(b) excessive formation of industrial units.
(c) excessive use of man – made compounds containing both fluorine and chlorine.
(d) excessive deforestation.
Answer:
(c) excessive use of man – made compounds containing both fluorine and chlorine.

Question 16.
Which of the following is a recently originated problem of environment?
(a) Ozone layer depletion.
(b) Green house effect.
(c) Global warming.
(d) All of the above.
Answer:
(d) All of the above.

Question 17.
When we breathe in air, nitrogen also goes inside along with oxygen. What is the fete of this nitrogen?
(a) It moves along with oxygen into the cells.
(b) It comes out with the CO₂ during exhalation.
(c) It is absorbed only by the nasal cells.
(d) Nitrogen concentration is already more in the cells so it is not at all absorbed.
Answer:
(b) It comes out with the CO₂ during exhalation.

Question 18.
Top – soil contains the following ___________ .
(a) Humus and living organisms only.
(b) Humus and soil particles only.
(c) Humus, living organisms and plants.
(d) Humus, living organisms and soil particles.
Answer:
(d) Humus, living organisms and soil particles.

Question 19.
Choose the correct sequences ___________ .
(a) CO₂ in atmosphere → decomposers → organic carbon in animals → organic carbon in plants.
(b) CO₂  in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil.
(c) Inorganic carbonates in water → organic carbon in plants → organic carbon in animals → scavengers.
(d) Organic carbon in animals → decomposers → CO₂ in atmosphere → organic carbon in plants.
Answer:
(b) CO₂  in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil.

Question 20.
Major source of mineral in soil is the ___________ .
(a) parent rock from which soil is formed.
(b) plants.
(c) animals
(d) bacteria.
Answer:
(a) parent rock from which soil is formed.

Natural Resources Very Short Answer Type Questions

Question 1.
Name the factor responsible for rainfall patterns in India.
Answer:
North – East or South – West Monsoons.

Question 2.
Name any two organisms. Which play important role in nitrogen – fixation.
Answer:
Rhizobium and Nitrosomonas.

Question 3.
State the process and the form by which carbon enters in the living system.
Answer:
Respiration.

Question 4.
Write any one difference between oxygen and ozone.
Answer:
Oxygen is diatomic (O₂) whereas ozone is triatomic (O₃).

Question 5.
What is the temperature range on the surface of moon?
Answer:
-190°C to 110°C.

Natural Resources Short Answer Type Questions

Question 1.
Rivers from land, add minerals to sea water. Discuss, how?
Answer:
Water is wonderful solvent. As water flows over the rocks which containing soluble minerals and these mineral get dissolved in the water. Thus, Rivers from land, add minerals to sea water.

Question 2.
How can we prevent the loss of top soil?
Answer:
Loss of top soil can be prevented by stopping the falling of trees and excessive grazing by animals, growing more the vegetation cover.

Question 3.
How is the life of organisms living in water affected when water gets polluted?
Answer:
When water gets polluted, oxygen does not dissolves in water properly, which effects the aquatic organisms adversely. Also, due to undesirable chemicals and waste discharge from factories and households cause diseases to the aquatic organisms.

Question 4.
During summer, if you go near the lake, you feel relief from the heat, why?
Answer:
Due to evaporation of water, air nearby water bodies become cooler.

Question 5.
In coastal area, wind current moves from the sea towards the land during day; but during night it moves from land to the sea. Discuss the reason.
Answer:
Air above the land gets heated quickly during day and starts rising. This creates a region of low pressure as a result air over sea rushes into this area of low pressure. This movement of air from one region to the other creates winds. During night, as water cools down slowly, the air above water is warmer than the air on land. So, air moves from land to sea creating winds.

Question 6.
Following are a few organisms: (a) lichen (b) mosses (c) mango tree (d) cactus.
Which among the above can grow on stones; and also help in formation of soil? Write the mode of their action for making soil.
Answer:
Lichens and Mosses: (a) and (b).
Lichens and mosses release materials which break down the stones causes formation of soil.

Question 7.
Soil formation is done by both abiotic and biotic factors. List the names of these factors by classifying them as abiotic and biotic?
Answer:

1. Sun, water and wind are abiotic factors that forms soil.
2. Lichens, mosses and trees are biotic factors which form soil.

Question 8.
All the living organisms are basically made up of C, N, S, P, H and O. How do they enter the living forms? Discuss.
Answer:
In 1952, Stanley Miller along with Harold C. Urey designed an experiment to see how complex organic molecules might have formed under the conditions of early Earth. From long experimental method he developed organic matter from non living things. And, concluded that on specific environmental conditions non living things grow up to living form.

Question 9.
Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?
Answer:
The percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere because cycling of these gases maintains consistency.

Question 10.
Why does moon have very cold and very hot temperature variations e.g., from -190°C to 110°C even though it is at the same distance from the sun as the earth is?
Answer:
No atmosphere exists on the moon thus, moon have very cold and very hot temperature variations e.g., from -190°C to 110°C even though it is at the same distance from the sun as the earth.

Question 11.
Why do people love to fly kites near the seashore?
Answer:
People love to fly kites near the seashore because air gets heated quickly during day and creates wind, which helps them to fly kites easily.

Question 12.
Why does Mathura refinery pose problems to the Taj Mahal?
Answer:
Polluted environment of Mathura due to refinery and other infrastructural facilities, industries etc. release toxic gases (like oxides of sulphur) which causes acid rain and corrode the marbles of Taj Mahal.

Question 13.
Why does water need conservation even though large oceans surround the land masses?
Answer:
Marine water is not useful for human and plant life directly. Hence fresh water need conservation. Uneven distribution of limited fresh water resources need conservation to ft ever rising demands.

Question 14.
There is mass mortality of fishes in a pond. What ma) the reasons?
Answer:

1. Thermal pollution
2. Addition of poisonous (mercury) compounds in water
3. Due to blockage of gills with any pollutant.

Natural Resources Long Answer Type Questions

Question 1.
How do fossil fuels cause air pollution?
Answer:
Most of air pollution of our environment is caused by the burning of fossil fuels, such as coal, oil natural gas and gasoline to produce electricity and power out vehicles. Carbon dioxide (CO₂) is a good indicator of how much fossil fuel is burnt and how much of other pollutants are emitted as a result. When fossil fuels are burnt, they release primarily nitrogen oxides into the atmosphere, which leads to the formation of smog and simultaneously acid rain.

The most common nitrogen – related compounds emitted into the air by human activities are collectively referred to as nitrogen oxides. Ammonia is also a harmful nitrogen compound emitted to the air, agricultural activities also contribute in air pollution but fossil fuels are most common reason for its increase day by day.

Question 2.
What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.
Answer:
Domestic and industrial waste dump to water – bodies are main reason of water pollution. Industries produce huge amount of waste which contains toxic chemicals and pollutants which can cause air pollution and damage us and our environment. They contain pollutants such as lead, mercury, sulphur, asbestos, nitrates and many harmful chemicals.

Prevention of water pollution:
Stop dumping waste in water – bodies is the only way to get clear water resources. Do not throw chemicals, oils, paints and medicines down the sink drain or the toilet. If you use chemicals and pesticides for your gardens and farms, be mindful not to overuse pesticides and fertilizers. This will reduce run offs of the chemical into nearby water sources.

Natural Resources Higher Order Thinking Skills (HOTS)

Question 1.
If decomposers are removed completely from the Earth, what will be the result? Give reasons.
Answer:
Decomposers are the organisms that feed on dead and decaying matter present on the Earth. These organisms decompose the dead plants and animals returning the complex nutrients present in them in available form to the nature.

Question 2.
Why is nitrogen – fixing bacteria found only in the roots of leguminous plants?
Answer:
The roots of leguminous plants contains root nodules. These nodules provide shelter to nitrogen fixing bacteria like Rhizobium.

Natural Resources Value Based Questions

Question 1.
Manisha lived near industrial area in Delhi. During winters . she saw that the smoke has reduced the visibility in the area. Manisha requested the industries to fit in chimney the precipitators that would not release smoke particulates in air.

1. What is smog?
2. Name two disease caused due to air pollution.
3. What values are displayed by Manisha?

Answer:

1. When smoke is added to fog, smog is formed.
2. Air – pollution causes respiratory problem and allergies.
3. Manisha showed the value of self-awareness, and responsible behaviour.

Question 2.
Radha saw a child sleeping in a car parked with closed doors and glass rolled up in the open area on a sunny day near the market. She immediately raised an alarm and with the help of police, she got the window glass rolled down.

1. Why was it not safe to keep the doors with window glass rolled Up for a child inside the car?
2. Name two gases that can lead to above effect.
3. What values are exhibited by Radha?

Answer:

1. It was not safe for the child in the car with locked doors and window rolled up, the sunlight would result in the green house effect in the car. This would increase the temperature in the car and also result in the increase in CO₂ level which would lead to suffocation.
2. Carbon dioxide gas and methane gas can lead to green house effect.
3. Radha displayed the value of aware citizen and responsible behaviour.

MP Board Class 9th Science Solutions

MP Board Class 9th Science Solutions Chapter 15 Improvement in Food Resources

Improvement in Food Resources Intext Questions

Improvement in Food Resources Intext Questions Page No. 204

Question 1.
What do we get from cereals, pulses, fruits and vegetables?
Answer:
We get carbohydrates from cereals and proteins from pulses. Fruits and vegetables give us lots of vitamins and minerals.

Improvement in Food Resources Intext Questions Page No. 205

Question 1.
How do biotic and abiotic factors affect crop production?
Answer:
Biotic factors like pests, insects etc. reduce the crop production. Pests harm crops by feeding over them. Weeds also reduce crop productivity by competing with the main crop for nutrients and light. Abiotic factors like wind, rain, temperature etc. impact the overall crop production. For example, droughts and floods almost completely destroy the whole crop of a particular area.

Question 2.
What are the desirable agronomic characteristics for crop improvements?
Answer:
The desirable agronomic characteristics for crop improvements are:

1. Tallness and profuse branching in any fodder crop.
2. Dwarf characteristics in cereals.

Improvement in Food Resources Intext Questions Page No. 206

Question 1.
What are macro – nutrients and why are they called macro – nutrients?
Answer:
Macro – nutrients are those nutrients which are required in large quantities for growth and development of plants. Since they are required in large quantities, they are known as macro – nutrients. The six macro – nutrients required by plants are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.

Question 2.
How do plants get nutrients?
Answer:
Plants consume nutrients from air, water and soil. Soil is one of the important sources of nutrients. Plants get thirteen nutrients from soil. The remaining three nutrients (carbon, oxygen, and hydrogen) are obtained from air and water.

Improvement in Food Resources Intext Questions Page No. 207

Question 1.
Compare the use of manure and fertilizers in maintaining soil fertility.
Answer:
Manures are biodegradable substances which increase soil fertility by enriching the soil with organic matter and nutrients as it is prepared by the decomposition of animal excreta and plant wastes.

On the other hand, fertilizers are mostly artificially developed inorganic compounds whose excessive use is harmful to ecosystems components and soil fertility. Hence, fertilizers are considered good only for short term use.

Improvement in Food Resources Intext Questions Page No. 208

Question 1.
Which of the following conditions will give the most benefits? Why?
(а) Farmers use high – quality seeds, do not adopt irrigation or use fertilizers.
(b) Farmers use ordinary seeds, adopt irrigation and use fertilizer.
(c) Farmers use quality seeds, adopt irrigation, use fertilizer and use crop protection measures.
Answer:
(c) Farmers using good quality seeds, adopting irrigation, using fertilizers and using crop protection measures will get most benefits.
Reasons are as follows:

1. Increases the total crop production as good quality seeds, then a majority of the seeds will germinate properly, and will grow into a healthy plants.
2. Proper irrigation will improve the water availability to crops.
3. Fertilizers promote high growth and development in plants by providing the essential nutrients such as nitrogen, phosphorus, potassium etc.
4. Crop protection measures include various methods to control weeds, pests and infectious agents.

Improvement in Food Resources Intext Questions Page No. 209

Question 1.
Why should preventive measures and biological control methods be preferred for protecting crops?
Answer:
Preventive measures and biological control methods should be preferred for protecting crops because excessive use of chemicals leads to environmental problems. Biological methods harm neither crops nor environment.

Question 2.
What factors may be responsible for losses of grains during storage?
Answer:
Factors causing loss of grains during storage:

1. Biotic Factors: Insects, rodents, fungi and bacteria etc.
2. Abiotic Factors: moisture content and temperature etc.

Improvement in Food Resources Intext Questions Page No. 210

Question 1.
Which method is commonly used for improving cattle breeds and why?
Answer:
Cross breeding is commonly used for improving cattle breeds. Cross breeding between two good varieties of cattle will produce a new improved variety. For example, the cross between foreign breeds such as Jersey Brown, Swiss and Indian breeds such as Red Sindhi, Sahiwal produces a new variety having qualities of both breeds.

Improvement in Food Resources Intext Questions Page No. 211

Question 1.
Discuss the implications of the following statement: “It is interesting to note that poultry is India’s most efficient converter of low fibre food stuff (which is unfit for human consumption) into highly nutritious animal protein food.”
Answer:
Poultry in India is the most efficient converter of low fibre food stuff in nutritious animal protein food. In poultry farming, domestic fowls are raised to produce eggs and chicken. For this, the fowls are given animal feeds in the form of roughage, which mainly consists of fibres. Thus, by feeding animals a fibre rich diet, the poultry gives highly nutritious food in the form of eggs and chicken.

Question 2.
What management practices are common in dairy and poultry farming?
Answer:
Common management practices in dairy and poultry farming are:

1. Proper shelter facilities and their regular cleaning.
2. Some basic hygienic conditions such as clean water, nutritious food etc.
3. Animals are kept in spacious, airy and ventilated place.
4. Prevention and cure of diseases at the right time is ensured.

Question 3.
What are the differences between broilers and layers and in their management?
Answer:
Layers are meant for egg production, whereas broilers are meant for poultry meat. Nutritional, environmental and housing conditions required by broilers are different from those required by egg layers. A broiler chicken, for their proper growth, requires vitamin rich supplements especially vitamin A and K. Also, their diet includes protein rich food and enough fat. They also require extra care and maintenance to increase their survival rate in comparison to egg layers.

Improvement in Food Resources Intext Questions Page No. 213

Question 1.
How are fish obtained?
Answer:
Fish can be obtained by two ways:

1. Capture fishing: It is the process of obtaining fish from natural resources.
2. Culture fishery: It is the practice of farming fishes. Farming can be done in both freshwater ecosystem (which includes river water, pond water) and marine ecosystem.

Question 2.
What are the advantages of composite fish culture?
Answer:
The advantages of composite fish culture are:

1. Fish can be grown in crop fields especially paddy.
2. Intensive fish farming is possible because plenty of water is available during crop seasons.
3. In this system, both local and imported fish species can be cultivated.

Question 3.
What are the desirable characters of bee varieties suitable for honey production?
Answer:
Bee varieties having the following desirable characters are suitable for honey production:

1. They should yield high quantity of honey.
2. They should not sting much.
3. They should stay in the beehive for long durations.
4. They should breed very well.

Question 4.
What is pasturage and how is it related to honey production?
Answer:
Pasturage is the availability of flowers from which bees collect nectar and pollen. It is related to the production of honey as it determines the taste and quantity of honey.

Improvement in Food Resources NCERT Textbook Exercises

Question 1.
Explain any one method of crop production which ensures high yield.
Answer:
Inter – cropping method ensures high yield of crop production. It is a practice of growing two or more crops simultaneously in the same field in rows. In inter – cropping, definite row patterns are followed such as one row of main crop is followed by two rows of inter – crop. In inter – cropping, there is a greater utilisation of the inter – spaced area, light, nutrients, water and air. As a result, productivity per unit area is increased.

Question 2.
Why are manures and fertilizers used in fields?
Answer:
Manures and fertilizers are used in fields to enrich the soil with the required nutrients. Manure helps in enriching the soil with organic matter and nutrients. This improves the fertility and structure of the soil. On the other hand, fertilizers ensure a healthy growth and development in plants. They are a good source of nitrogen, phosphorus and potassium. To get an optimum yield, it is instructed to use a balanced . combination of manures and fertilizers in the soil.

Question 3.
What are the advantages of inter-cropping and crop rotation?
Answer:
Inter – cropping and crop rotation, both are used to get maximum benefit on limited land. Inter – cropping helps in preventing pests and diseases to spread throughout the field. It also increases soil fertility, whereas crop rotation prevents soil depletion, increases soil fertility and reduces soil erosion. Both of these methods reduce the need for fertilizers. They also helps in controlling weeds and the growth of pathogens and pests in crops.

Question 4.
What is genetic manipulation? How is it useful in agricultural practices?
Answer:
Genetic manipulation is a process where the gene for a particular character is introduced inside the chromosome of a cell. When the gene for a particular character is introduced in a plant cell, a transgenic plant is produced. These transgenic plants exhibit characters governed by the newly introduced gene.

Genetic manipulation is useful in developing varieties with higher yield, good quality, biotic and abiotic resistance, short maturity period, wider adaptability and desirable agronomic characteristics.

Question 5.
How do storage grain losses occur?
Answer:
There are many biotic and abiotic factors that harm stored grains and result in degradation, poor germinability, discolouration etc. which leads to storage grain losses. Biotic factors like insects or pests cause direct damage by feeding on seeds.

They also deteriorate and contaminate the grain, making it unfit for further consumption.  Abiotic factors such as temperature, light, moisture etc., also affect storage food. They decrease the germinating ability of the seeds and make them unfit for future use by farmers. Unpredictable occurrence of droughts and floods also causes destruction of crops.

Question 6.
How do good animal husbandry practices benefit farmers?
Answer:
Cattle farming is one of the methods of animal husbandry that is most beneficial for farmers. Better breeds of draught animals can be produced. Such draught animals are engaged in agricultural fields for labour such as carting, irrigation, tilling, etc.

Question 7.
What are the benefits of cattle farming?
Answer:
Benefits of cattle farming:

1. Good quality and quantity of dairy products can be produced.
2. Draught labour animals can be raised for agricultural work.
3. New breed of animals that are resistant to diseases can be raised by crossing two breeds with the desired traits.

Question 8.
For increasing production, what is common in poultry, fisheries and bee – keeping?
Answer:
Proper management techniques are the common factors for increasing production in poultry, fisheries and bee keeping. Regular cleaning of farms is of importance. Also, maintenance of temperature and prevention and cure of diseases in farming is also required to increase the growth of animals.

Question 9.
How do you differentiate between capture fishing, mariculture and aquaculture?
Answer:

1. Capture fishing is the method to obtain fishes from natural resources like rivers, ponds, waterfalls etc.
2. Mariculture is the culture of marine fishes for commercial use.
3. Aquaculture involves the production of aquatic animals that are of high economic value such as prawns, lobsters, fishes, crabs etc.

Improvement in Food Resources Additional Questions

Improvement in Food Resources Multiple Choice Questions

Question 1.
Which one is an oil yielding plant among the following?
(a) Lentil
(b) Sunflower
(c) Cauliflower
(d) Hibiscus.
Answer:
(b) Sunflower

Question 2.
Which one is not a source of carbohydrate?
(a) Rice
(b) Millets
(c) Sorghum
(d) Gram.
Answer:
(d) Gram.

Question 3.
Find out the wrong statement from the following:
(a) White revolution is meant for increase in milk production.
(b) Blue revolution is meant for increase in fish production.
(c) Increasing food production without compromising with environmental quality is called as sustainable agriculture.
(d) None of the above.
Answer:
(d) None of the above.

Question 4.
To solve the food problem of the country, which among the following is necessary?
(a) Increased production and storage of food grains.
(b) Easy access of people to the food grain.
(c) People should have money to purchase the grains.
(d) All of the above.
Answer:
(d) All of the above.

Question 5.
Find out the correct sentence.
(i) Hybridisation means crossing between genetically dissimilar plants.
(ii) Cross between two varieties is called as inter specific hybridisation.
(iii) Introducing genes of desired character into a plant gives genetically modified crop.
(iv) Cross between plants of two species is called as inter varietal hybridisation.
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (ii) and (iii)
(d) (iii) and (iv).
Answer:
(a) (i) and (ii)

Question 6.
Weeds affect the crop plants by
(a) killing of plants in field before they grow.
(b) dominating the plants to grow.
(c) competing for various resources of crops (plants) causing low availability of nutrients.
(d) all of the above.
Answer:
(c) competing for various resources of crops (plants) causing low availability of nutrients.

Question 7.
Which one of the following species of honey bee is an Italian species?
(a) Apis dorsata
(b) Apis florae
(c) Apis cerana indica
(d) Apis mellifera.
Answer:
(d) Apis mellifera.

Question 8.
Find out the correct sentence about manure
(ii) Manure contains large quantities of organic matter and small quantities of nutrients.
(ii) It increases the water holding capacity of sandy soil.
(iii) It helps in draining out of excess of water from clayey soil.
(iv) Its excessive use pollutes environment because it is made of animal excretory waste.
(a) (i) and (iii)
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (iii) and (iv).
Answer:
(b) (i) and (ii)

Question 9.
Cattle husbandry is done for the following purposes:
(i) Milk production
(ii) Agricultural work
(iii) Meat production
(iv) Egg production.
(a) (i), (ii) and (iii)
(b) (ii), (iii) and (iv)
(c) (iii) and (iv)
(d) (i) and (iv).
Answer:
(a) (i), (ii) and (iii)

Question 10.
Which of the following are Indian cattle?
(i) Bos indicus
(ii) Bos domestica
(iii) Bos bubalis
(iv) Bos vulgaris.
(a) (i) and (iii)
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (iii) and (iv).
Answer:
(a) (i) and (iii)

Question 11.
Which of the following are exotic breeds?
(i) Brawn
(ii) Jersey
(iii) Brown Swiss
(iv) Jersey Swiss.
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv).
Answer:
(b) (ii) and (iii)

Question 12.
Poultry farming is undertaken to raise the following:
(a) Egg production
(b) Feather production
(c) Chicken meat
(d) Milk production.
Answer:
(a) Egg production

Question 13.
Poultry fowl are susceptible to the following pathogens:
(a) Viruses
(b) Bacteria
(c) Fungi
(d) All of the above.
Answer:
(d) All of the above.

Question 14.
Which one of the following fishes is a surface feeder?
(a) Rohus
(b) Mrigals
(c) Common carps
(d) Catlas.
Answer:
(d) Catlas.

Question 15.
Animal husbandry is the scientific management of ___________ .
(i) animal breeding
(ii) culture of animals
(iii) animal livestock
(iv) rearing of animals
(a) (i), (ii) and (iii)
(b) (ii), (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (i), (iii) and (iv).
Answer:
(d) (i), (iii) and (iv).

Improvement in Food Resources Very Short Answer Type Questions

Question 1.
Match the column A with the column B

Answer:
(a) (ii)
(b) (iii)
(c) (i)
(d) (iv).

Question 2.
Fill in the blanks.

1. Pigeon pea is a good source of ___________ .
2. Berseem is an important ___________ crop.
3. The crops which are grown in rainy season are called ___________ crops.
4. ___________ are rich in vitamins.
5. ___________ crop grows in winter season.

Answer:

1. protein
2. fodder
3. Kharif
4. vegetables
5. Rabi.

Question 3.
State any one importance of photoperiod in agriculture.
Answer:
Photoperiod is important for growth of plants and flowering.

Question 4.
What are desirable traits for fodder crop?
Answer:

1. Profused branching.
2. Tall Plants.

Question 5.
White revolution in India has made us self – sufficient in a product. Name it.
Answer:
Milk.

Improvement in Food Resources Short Answer Type Questions

Question 1.
What is a GM crop? Name any one such crop which is grown in India.
Answer:
Crop developed artificially with the help of modern biotechnology to obtain the desired character is called as genetically modified(GM) crop. But, cotton and egg plant are examples of GM crops which are resistant to many harming biological factors.

Question 2.
List out some useful traits in improved crop.
Answer:
Useful traits in improved crops are as follows:

1. better yield.
2. improved quality.
3. resistance to biotic and abiotic factors.
4. better adaptability.
5. better economically.

Question 3.
Why is organic matter important for crop production?
Answer:
Organic matter is important for crops because a fertile and healthy soil is the basis for healthy plant’s growth and soil organic matter works as a foundation for healthy and productive soils.
It helps soil by:

1. improving soil structure.
2. increasing water holding capacity of soil.
3. drainage and in avoiding water logging.
4. giving shelter to number of animals which also improve soil’s nutrients value.

Question 4.
Why is excessive use of fertilizers detrimental for environment?
Answer:
Excessive use of fertilizers is harmful because it is artificial in origin and accumulate in biological cycle and disturb its balance which causes environmental pollution as their residual and unused amounts will become pollutants for air, water and soil.

Question 5.
Give one word for the following:

1. Farming without the use of chemicals as fertilizers, herbicides and pesticides is known as ___________ .
2. Growing of wheat and groundnut on the same field is called as ___________ .
3. Planting soyabean and maize in alternate rows in the same field is called as ___________ .
4. Growing different crops on a piece of land in preplanned succession is known as ___________ .
5. Xanthium and Parthenium are commonly known as ___________ .
6. Causal organism of any disease is called as

Answer:

1. organic farming
2. mixed farming
3. inter – cropping
4. crop rotation
5. weeds
6. pathogens

Question 6.
Match the following A and B:

Answer:
(a) (iii)
(b) (v)
(c) (iv)
(d) (i)
(e) (ii).

Question 7.
Define the term hybridization and photoperiod.
Answer:

1. Hybridization: Hybridization is the process in which two genetically different individuals are crossed to result generally into an individual with a desired trait.
2. Photoperiod: Photoperiod in plants is defined as the developmental responses towards the comparative lengths of light and dark periods in its region.

Question 8.
Fill in the blanks:

1. Photoperiod affects the ___________ .
2. Kharif crops are cultivated from ___________ to ___________ .
3. Rabi crops are cultivated from ___________ to ___________ .
4. Paddy, maize, green gram and black gram are ___________ crops.
5. Wheat, gram, pea, mustard are ___________ crops.

Answer:

1. flowering
2. June to October
3. November to March,
4. Kharif
5. Rabi

Question 9.
Cultivation practices and crop yield are related to environmental condition. Yes/No? Give reasons.
Answer:
Environmental conditions are the components which influence plant growth and genetic factors. Environmental factors include everything in our surrounding i.e. air, water, temperature, atmospheric pressure, surrounding gases etc. When we cultivate any plant or consider crop growth, we check all the above environmental factors before sowing. Hence yes, cultivation practices and crop yield are related to environmental condition.

Question 10.
Fill in the blanks:

1. A total of ___________ nutrients are essential to plants.
2. ___________ and ___________ are supplied by air to plants.
3. ___________ is supplied by water to plants.
4. Soil supplies ___________ nutrients to plants.
5. nutrients are required in large quantity and called as ___________ .
6. nutrients are needed in small quantity for plants and are called ___________ .

Answer:

1. sixteen
2. Oxygen and carbon
3. Hydrogen
4. thirteen
5. Six, macro – nutrients
6. Seven, micronutrients

Improvement in Food Resources Long Answer Type Questions

Question 1.
Define:

1. Vermicompost
2. Green manure
3. Bio fertilizer.

Answer:

1. Vermicompost: Vermicomposting is the process in which worms and micro – organisms are used to turn organic waste into a black, earthy – smelling, nutrient – rich humus.
2. Green manure: When crop or plant that is grown and then intentionally plowed under to improve the underlying soil, it is called green manure.
3. Bio fertilizer: Fertilizer created from biological components as small plants.

Question 2.
Discuss various methods for weed control.
Answer:
Unwanted plants which grow along with crops are called weeds. They compete with the crop plants for light, water, space and minerals, and harm their growth and yield. Some of them produce poisonous substances which can harm the growth of the crop or poison the produce.

Removing weeds from a field is called weeding. It can be done Manually or by using an implement like a trowel, hoe or rake. A third way of getting rid of weeds is by spraying chemicals called weedicides. These chemicals destroy the weeds but not the crop plants.

Improvement in Food Resources Higher Order Thinking Skills (HOTS)

Question 1.
Why should our food contain cereals, pulses, fruits and vegetables?
Answer:

1. Cereals provide carbohydrates for energy requirements.
2. Pulses give proteins.
3. Fruits and vegetables provide various vitamins and minerals.

Question 2.
Why moisture level of food grains should be checked before their storage?
Answer:
Before storage, moisture level of food grains should not be more than 9% otherwise growth of micro – organisms (bacteria and fungi) will take place causing either discolouration or complete spoilage of food grains.

Improvement in Food Resources Value Based Questions

Question 1.
A group of Eco Club students made a compost pit in the school. They collected all bio – degradable waste from the school canteen and used it to prepare the compost

1. Name two waste that can be used for the compost and two wastes obtained from canteen which cannot be used for the compost making.
2. What is the other important compound required for making the compost?
3. State the values of Eco Club students.

Answer:

1. Two waste used for compost are vegetable peels, fruit peels and pulps. Two waste materials that cannot be used as compost are pickels and curd.
2. Bacteria present in soil are used as component for making compost.
3. Eco club students reflect the value of group workers and responsible citizens.

Question 2.
In a poultry farm, large number of birds died. Farm owner was unable to identify the reason and thought someone has done it intentionally. Aryan living nearby his farm noticed that the conditions in the farm were very unhygienic and poor ventilation was there.

1. What do you think can be the reason for these deaths?
2. What measures can be followed to prevent this in future?
3. What values are shown by Aryan?

Answer:

1. The conditions of the farm were unhygienic and ventilation was also poor. These may be the possible reasons.
2. These conditions should be improved. Proper food, hygiene practices and good ventilation should be there to prevent this.
3. The values of awareness and carefullness are shown by Aryan.

MP Board Class 9th Science Solutions

MP Board Class 9th Maths Solutions Chapter 9 Areas of Parallelograms and Triangles Ex 9.1

Question 1.
Which of the following figures lie on the same base and between the same parallels. In such a case, write the common base and the two parallels.

Solution:
(i) Base DC, Parallels DC and AB
(iii) Base QR, Parallels QR and PS
(v) Base AD, Parallels AD and BQ.

MP Board Class 9th Maths Solutions

MP Board Class 9th Maths Solutions Chapter 8 Quadrilaterals Ex 8.2

Question 1.
ABCD is quadrilateral in which P, Q, R and S are mid-point^jf the sides AB, BC, CD and DA (see Fig.). AC is a diagonal. Show that:

1. SR ∥ AC and SR = \(\frac{1}{2}\) AC
2. PQ = SR
3. PQRS is a parallelogram.

Solution:
Given
ABCD is in which P, Q, R and S are the mid-points of sides AB,BC, CD and DA.
To prove.

1. SR ∥ AC and SR= \(\frac{1}{2}\) AC
2. PQ = SR
3. PQRS is a parallelogram.

Proof:
In ∆ABC. P is the mid point of AB and Q is the midpoint of BC.
∴ PQ ∥ AC and PQ = \(\frac{1}{2}\) AC (by MPT)…(1)
In ∆ADC, S is the mid-point of AD and R is the mid – point of DC.
SR ∥ AC and SR = \(\frac{1}{2}\) AC (by MPT)…(2)

1. SR ∥ AC and SR = \(\frac{1}{2}\) AC (proved)
2. PQ ∥ AC and SR = \(\frac{1}{2}\) AC
∴ PQ = SR
3. From (1) and (2), we get
PQ ∥ SR and PQ = SR
∴ PQRS is a parallelogram

Question 2.
ABCD is a rhombus and P, Q, R and S are the mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral P&RS is a rectangle.
Solution:
Given
ABCD is rhombus and P, Q and R and S are the mid-points of sides AB, BC, CD and DA.
To prove
PQRS is a rectangle.
Construction:
Join AC and BD).

Proof:
In ∆ABC, P is the midpoint of AB and Q is the midpoint of BC.
∴ PQ ∥AC (By MPT) …(1)
In ∆ADC, S is the midpoint of AD and R is the midpoint of DC.
SR ∥ AC (By MPT) …(2)
From (1) and (2), we get
PQ ∥ SR …(3)
In ∆ABD, P is the midpoint of AB and S is the midpoint of AD.
PS ∥ BD …(4)
In ABCD, Q is the midpoint of BC and R is the midpoint of CD
∴ QR ∥ BD (ByMPT) …(5)
From (4) and (5), we get
PS ∥ QR …(6)
In quadrilateral PQRS, PQ ∥ SR and PS ∥ QR
∴ PQRS is a parallelogram.
In quadrilateral OESF
SF ∥ EO (∴ SR ∥ AO …(7)
SE ∥ FO (∴ SP ∥ BD) …(8)
SEOF is a parallelogram.
We know that, that in a parallelogram opposite angles are equal.
∴ ∠ESF = ∠EOF= 90°
(∴ In a rhombus, diagonals intersect each other at right angles)
Hence, PQRS is a rectangle.

Question 3.
ABCD is a rectangle and P,Q,R and S are mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rhombus.
Given
ABCD is a rectangle P,Q,R and S are the mid-points of AB, BC, CD and DA.
To prove.
PQRS is a rhombus.
Proof:
In ∆ABC, P is the midpoint of AB and Q is the midpoint of BC.

PQ ∥ AC and PQ = \(\frac{1}{2}\) AC (By MPT) ….(1)
In ∆ADC, S is the midpoint of AD and R is the midpoint of DC.
∴ SR ∥ AC and SR = \(\frac{1}{2}\) AC (By MPT)…(2)
From (1) and (2),we get
PQ ∥ SB and PQ = SR
PQRS is a parallelogram
AD = BC (∴ ABCD is a rectangle)
⇒ \(\frac{1}{2}\) AD = \(\frac{1}{2}\) BC
AS = BQ
In ∆PAS and ∆PBQ, AS = BQ (proved)
AP = BP P is the mid-point of AB
∠A = ∠B (each 90°)
and so PS = PQ (ByCPCT)
In a ∥^gm, if adjacent sides are equal, then it a rhombus.
∴ PQRS is a rhombus.

Question 4.
ABCD is a trapezium in which AB ∥ DC, BD is a diagonal and E is the mid-point of AD. A line is drawn through E parallel to AB intersecting BC and F (see Fig. below). Show that F is the mid-point of BC.

Solution:
Given
AB ∥ DC, DE = AE and EF ∥ AS.
To prove
F is the mid-point of BC
Proof:
AB ∥ DC (given) …(1)
AB ∥ EF (given) …(2)

From (1) and (2) we get,
DC ∥ EF
In ∆ABD, E is the mid – point of AD
EP ∥ AB (∴ EF∥AB)
∴ P is the mid – point of BD (By CMPT)
In ∆BCD, P is the midpoint of BD.
PF ∥ DC (∴ EF ∥ DC)
F is the midpoint of BC (By CMPT).

Question 5.
In a parallelogram ABCD, E and F are the mid-point of sides AB and CD respectively (See Fig.). Show that the line segments AD and EC trisect the diagonal BD.

Solution:
Given
ABCD is a ∥^gm, E and F are the mid-point of AB and CD.
To prove:
BQ = PQ = DP
Proof:
AB ∥ DC and AB = DC (∴ ABCD is a ∥gm)
⇒ \(\frac{1}{2}\) ∥ AB \(\frac{1}{2}\) DC and \(\frac{1}{2}\) AB = \(\frac{1}{2}\)DC
⇒ AE ∥ FC and AE = FC (∴ \(\frac{1}{2}\) AB = AE and \(\frac{1}{2}\) DC = FC)
AECF is a parallelogram (∴ AECF is a ∥^gm)
In ∆ABP, E is the mid – point of AB,
EQ ∥AP (∴ AECF is a ∥<sup<gm)

∴ Q is the midpoint of BP (∴ by CMPT) …(1)
BQ = PQ
In ∆DQC, F is the midpoint of DC
EF ∥ CQ AECF is a ∥<sup<gm)
P is the midpoint of DQ
i.e., DP = PQ
From (1) and (2), we get BQ = PQ = DP.

Question 6.
Show that the line segments joining the mid-points of the opposite sides of a quadrilateral bisect each other.
Solution:
Given
ABCD is a in which P, Q.R and S are the mid-points of AB, BC, CD and DA respectively.
To prove
PR and SQ bisect each other.
Construction:
Join AC. Join PQ, QR, RS and SP.

Proof:
In ∆ABC, P is the midpoint of AB and Q is the midpointof BC.
PQ ∥ AC and PQ = \(\frac{1}{2}\) AC (By MPT) …..(1)
In ∆ADC, S is the midpoint of AD and R is the midpoint of DC.
SR ∥ AC and SR = \(\frac{1}{2}\) AC (by MPT) …(2)
Form (1) and (2), we get
PQ ∥ SR and PQ = SR
∴ PQRS is a parallelogram in which PR and SQ are diagonals^ and so PR and SQ bisect each other (In a ∥^gm, diagnaols bisect each other)

Question 7.
ABC is a triangle right angled at C. A line through the mid-point M of hypotenuse AB and parallel to BC intersects AC at D. Show that

1. D is the mid – point of AC
2. MD ⊥ AC
3. CM = MA = \(\frac{1}{2}\) AB.

Solution:
Given
ABC is a right ∆. ∠C = 90°
AM = BM and MD ∥ BC.
To prove:

1. D is the mid-point of AC, i.e., AD – CD
2. MD ⊥ AC
3. CM = MA = \(\frac{1}{2}\) AB

Proof:
1. In ∆ACB, M is the mid-point of AB and MD ∥ BC
∴ D is the mid – point of AC (By CMPT)
i.e., AD = CD

2. MD ∥ BC and AC is the transversal
∴ ∠ADM = ∠ACB (CA’s)
⇒ ∠ADM = 90° (∠ACB = 90°)
∴ MD ⊥ AC

3. In ∆ADM and ∆CDM,
AD = CD (proved)
∠ADM = ∠CDM (each 90°)
[∴ ∠ADM + ∠CDM = 180° (LPA’s); 90° + ∠CDM= 180°; ∠CDM = 90°]
MD = MD (common)
∴ ∆ADM = ∆CDM (By SAS)
and so MA = MC (By cpct) …(1)
MA = \(\frac{1}{2}\) AB (Given) …(2)
Form (1) and (2), we get MA = MC = \(\frac{1}{2}\) AB.

MP Board Class 9th Maths Solutions

MP Board Class 7th Science Solutions Chapter 14 Electric Current and its Effects

Electric Current and its Effects Intex Questions

Question 1.
Paheli and Boojho wonder whether the batteries used in tractors, trucks and inverters are also made from cells. Then why is it called a battery? Can you help them to find the answer to this question?
Answer:
The battery used in tractors, trucks and inverters is a combination of several cells. The cells are not dry cells. These are the several sets of plates and each set of plates acts like a cell.

Question 2.
Paheli and Boojho saw a magic trick sometime back. The magician placed an iron box on a stand. He then called Boojho and asked him to lift the box. Boojho could easily lift the box. Now the magician made a show of moving his stick around the box while muttering some thing. He again asked Boojho to lift the box. This time Boojho could not even move it. The magician again muttered some thing and now Boojho could lift the box? The audience, including Paheli and Boojho, were very impressed with the show and felt that the magician had some supernatural powers. However, after reading this chapter Paheli is wondering if the trick was indeed some magic or some science was involved? Can you guess what science might be involved?
Answer:
The magician arranged an electromagnet below the box. The electromagnet could be turned ‘ON’ and ‘OFF’ as when the magician signals his assistance. When the electromagnet is turned ‘ON’ it attracts the iron box and hence it could not be lifted.

Electric Current and its Effects Text Book Exercises

Question 1.
Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery?
Answer:

Question 2.
Draw the circuit diagram to represent the circuit shown in fig?

Answer:

Question 3.
Fig. shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells?

Answer:

Question 4.
The bulb in the circuit shown in figure, does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow?

Answer:
The problem with the circuit is that both the negative terminals are connected to the bulb. The corrected diagram is shown below:

Question 5.
Name any two effects of electric current?
Answer:
The two effects of electric current are heating effect and magnetic effect.

Question 6.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain?
Answer:
When electric current passes through a wire, it behaves like a magnet. This is the magnetic effect of the electric current due to attraction of the wire. So, the compass needle which is a magnet, gets deflected.

Question 7.
Will the compass needle show deflection when the switch in the circuit shown by fig is closed?

Answer:
No, because there is no cell so no current will flow.

Question 8.
Fill in the blanks:

1. Longer line in the symbol for a cell represents its ………………………… terminal.
2. The combination of two or more cells is called a …………………………..
3. When current is switched ‘on’ in a room heater, it ………………………..
4. The safety device based on the heating effect of electric current is called a ………………………

Answer:

1. Positive
2. Battery
3. Get heated
4. Fuse.

Question 9.
Mark T if the statement is true and F if it is false:

1. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.
2. When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks.
3. An electromagnet does not attract a piece of iron.
4. An electric bell has an electromagnet.

Answer:

1. False
2. True
3. False
4. True

Question 10.
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain?
Answer:
No, the plastic bags do not get attracted by the magnet, so they cannot be separated by an electromagnet. The plastic bags are not magnetic materials, only magnetic materials like iron can be attracted by magnet.

Question 11.
An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response?
Answer:
No, because this piece of wire will not melt even if high current flows through it. So, it will not prevent the damage done by high current.

Question 12.
Zubeda made an electric circuit using a cell holder shown in figure a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit?

Answer:
It is important to put the cells in right series. The positive terminal of the cell should be connected with negative terminal of the second cell. The switch should be closed properly and bulb should not be fused. If Zubeda will check these then the bulb will certainly glow. Also, in the circuit, there is no any bulb and switch, the connecting wires are not connected with bulb and switch.

Question 13.
In the circuit shown in Fig?
Answer:

1. Would any of the bulb glow when the switch is in the ‘OFF’ position?
2. What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Answer:

1. No, bulb will glow.
2. The bulb A will glow first, follow by bulb B and then bulb C, because bulb A comes first in the path of electric current flowing from positive terminal towards the negative terminal of the battery.

Extended Learning – Activities and Projects

Question 1.
Set up the circuit shown in Fig. again. Move the key to ‘ON’ position and watch carefully in which direction the compass needle gets deflected. Switch ‘OFF’ the current. Now keeping rest of the circuit intact, reverse the connections at the terminal of the cell. Again switch ‘on’ the current. Note the direction in which the needle gets deflected. Think of an explanation?

Answer:
When the connection of cell is reversed, the compass needle moves in opposite direction. This shows that the polarity of the magnet depends on the direction of current.

Question 2.
Make four electro – magnets with 20, 40, 60 and 80 turns. Connect them one by one to a battery of 2 cells. Bring the electromagnet near a box of pins. Count the number of pins attracted by it. Compare the strengths of the electromagnets?
Answer:
The strength increases with number of turns in the coil.

Question 3.
Using an electromagnet, you can make a working model of a railway signal as shown in Fig?
Answer:
Do with the help of your subject teacher.

Question 4.
Visit an electric shop. Request a mechanic to show you the various types of fuses and MCB and to explain how they work?

Answer:
Go and visit the nearby shop with your friends.

Electric Current and its Effects Additional Important Questions

Objective Type Questions

Question 1.
Choose the correct alternative:

Question (a)
The electric circuit which is broken at some point is called?
(a) closed
(b) open
(c) short
(d) None of these.
Answer:
(b) open

Question (b)
The amount of heat produced in a wire depends on its?
(a) material
(b) length
(c) thickness
(d) all of these.
Answer:
(d) all of these.

Question (c)
The direction of flow of conventional current is taken as
(a) -ve to +ve
(b) +ve to -ve
(c) both of these
(d) None of these.
Answer:
(b) +ve to -ve

Question 2.
Fill in the blanks:

1. A continuous flow of electric charge is called ………………………….
2. In a dry cell energy is converted into ……………………… energy.
3. A combination of two or more cells is called a ………………………
4. The positive terminal of one cell is connected to the ……………………. terminal of the next cell.
5. When the switch of a circuit is in the OFF position, the circuit is ………………………..
6. In the bulb, thin wire is called …………………………….
7. Current flowing in our household appliances is ………………………….
8. A ………………………. is a safety device which prevents damages to electrical circuits and possible fires.
9. The switches which automatically turn off when current in a circuit exceeds the safe limit are called ……………………….

Answer:

1. Current
2. Chemical, electrical
3. Battery
4. Negative
5. Incomplete
6. Filament
7. A.C.
8. Fuse
9. MCB

Question 3.
Which of the following statements are true (T) or false(F):

1. Switch is used to regulate the current.
2. An electric cell has three terminals.
3. Two or more than two cells are interconnected to make a battery.
4. The coil of wire in a electric iron is called an element.
5. Never use just any wire or strip of metal in place of a fuse.
6. Heating effect of electric current is used in a heater.
7. An electric bell is an application of an electromagnet.
8. A cell or a battery are the sources of electric current in an electric circuit.

Answer:

1. True
2. False
3. True
4. True
5. True
6. True
7. True
8. True.

Electric Current and its Effects Very Short Answer Type Questions

Question 1.
What is meant by electric current?
Answer:
The flow of negative charges i.e., electrons is called electric current.

Question 2.
Name the various sources of electric current?
Answer:
Cells and storage batteries.

Question 3.
What do you mean by electrically neutral substances?
Answer:
Those substances which have an equal quantity of positive and negative charge.

Question 4.
What are the two kinds of electric charges?
Answer:
The two kinds of electric charges are positive and negative.

Question 5.
Which terminal of a cell is represented by longer line?
Answer:
Positive.

Question 6.
Where should be the key placed in a circuit?
Answer:
The key or switch can be placed anywhere in the circuit.

Question 7.
What is an open electric circuit?
Answer:
An electric circuit having the switch in off position is called open electric circuit.

Question 8.
What is a closed electric circuit?
Answer:
An electric circuit having the switch in on position is called a closed circuit or a complete circuit.

Question 9.
What is the significance of using symbols in an electric circuit?
Answer:
Using symbols is significant as if we have to show the various batteries, bulbs and switches as they actually look, it would be very cumber some and take a lot of time.

Question 10.
What is a filament?
Answer:
In the bulb there is a thin wire, called the filament, which glows when an electric current passes through it.

Question 11.
What is the full form of CFL?
Answer:
Compact Fluoroscent Lamp.

Question 12.
What is the full form of MCB?
Answer:
Miniature Circuit Breaker.

Question 13.
What are different hazards of electricity?
Answer:

1. ‘Electric shock’
2. Tire due to short circuiting’.

Question 14.
List the appliances around you that depend on electricity for their operation. List the appliances that do not use electrical energy?
Answer:
Appliances that depend on electricity : Electric iron, Television, Geysers, Kitchen blender. Appliances that do not use electricity: Solar cells, Sewing Machine, Vehicles.

Question 15.
What energy is converted to electrical energy in a cell?
Answer:
Chemical energy is converted to electrical energy.

Question 16.
Name the three components of the cable used in a house circuit?
Answer:
The cable used in a house circuit has three cores of different colours. The red wire is the live wire. The black is the neutral wire and the green is the earth wire.

Question 17.
What kind of energy transformation takes place in an electric heater?
Answer:
In electric heater, electric energy is converted into heat energy.

Question 18.
Why is alternating current of same voltage more dangerous than direct current?
Answer:
The alternating current of same voltage is more dangerous than direct current because the direction and magnitude of AC changes alternatively and it may produce electric shock.

Question 19.
What happens when fuse melts away?
Answer:
When fuse melts away, the circuit is broken and the flow of current stops.

Question 20.
What is the main purpose of earthing an electrical appliance?
Answer:
To prevent electric shock.

Question 21.
Why is mica used in elements of an Electric iron?
Answer:
Mica is a insulator.

Question 22.
List the appliances in your house that do not have ground wires?
Answer:
Electric grinder, electric heater, electric oven, electric toaster.

Question 23.
Who discovered magnetic effect of electric current?
Answer:
Hans Christian Oersted.

Question 24.
What are the various effects shown by electricity?
Answer:

1. Heating Effect
2. Chemical Effect
3. Magnetic Effect.

Question 25.
What is electrolysis?
Answer:
The phenomenon of breaking up of a chemical compound under the action of electric current is called electrolysis.

Question 26.
What causes heating effect in electric appliances?
Answer:
Heating effect is produced by heating element i.e., mainly ‘Nichrome’ which is an alloy of nickel and chromium.

Question 27.
Why is ‘Nichrome’ most commonly used as heating element?
Answer:
Since ‘Nichrome’ has a very high melting point, it does not melt with the flow of current.

Question 28.
Name few processes which are based on chemical effect of electricity?
Answer:
Electroplating, Refining of metals and electrolysis of water.

Question 29.
What is meant by magnetic effect of current?
Answer:
A current carrying wire behaves like a magnet.

Electric Current and its Effects Short Answer Type Questions

Question 1.
Can electrically neutral substances be made to acquire charge?
Answer:
Yes, the delicate balance between the charges can be disturbed. Thus electrically neutral substances can be made to acquire charge. For example, if we rub a glass rod with silk we brush off some negative charges from the rod. The rod now acquires a net positive charge because it has more positive charges than negative.

Question 2.
What happens when a charged electroscope is connected into a uncharged electroscope by a wire? What is that called?
Answer:
When a charged electroscope is joined to a uncharged electroscope by a wire, charges flow from the charged to the uncharged electroscope through the wire till they are equalised. This flow of charges form an Electric Current.

Question 3.
What are the differences between a simple cell and a storage cell?
Answer:
A simple cell:

1. Once the chemicals are used up the cell stope supplying current.
2. A small amount of current can be drawn.

A storage cell:

1. The used up chemicals can be restored to their original state by reversing the reaction.
2. A large current can be drawn.

Question 4.
What should be the characteristics of an ideal heating element and that of an ideal safety fuse?
Answer:

1. Firstly the heating element should have a very high melting point.
2. Secondly, it should be a conductor.
3. Thirdly it should have high resistance.
4. The ideal safety fuse should be firstly it should have low melting point.
5. Secondly, it should be a conductor.
6. Thirdly, it have low resistance.

Question 5.
Make a list of materials around you which conduct electricity and a list of those that do not.
Answer:
Conductors of electricity are:
All metals, acid, base and salt solutions, aluminium, iron, copper, nickel. Do not conduct electricity are: Paper, rubber, wood, nylon, polythene, bakelite.

Question 6.
What is the significance of the earth wire?
Answer:
The metallic body of an electric appliance is connected to the earth through this earth wire. Sometimes due to faulty wire, the insulation breaks and the live w;re comes into contact with the body of appliance. If the appliance is earthed the charge will quickly flow to the earth, thus protecting us from electric shock.

Question 7.
How does fuse act as a safety device?
Answer:
A fuse is a porcelain holder having a short and thin piece of wire in it called fuse wire which easily melts on heating. Sometimes the insulation of a wire is broken i.e., live wire touches the neutral wire there is a short circuit. When there is a short circuit the fuse wire melts due to heating produced by the high current. The circuit is then broken and the current stops flowing. So damages are prevented.

Question 8.
On which effect of current does the fuse wire in electric circuits depend? Write two characteristics of a good quality fuse wire?
Answer:
Whenever a current passes through a material, a part or whole of its energy is converted into heat. The part which heats up is called heating elements. An alloy of nickel and chromium called Nichrome is one of the most heating elements.
Two characteristics of a good quality fuse wire are as follows:

1. It should have low melting point.
2. Is should have high specific resistance.

Question 9.
Write four safety measures to be taken while working with live electric lines?
Answer:

1. Do not touch the switch in the main switch board.
2. Do not cut the cable of an appliance with a pair of scissors when the appliance is switched on.
3. Do not touch any electric poles in the street, especially during the rainy season.
4. Do not touch any appliance (when it is switched on) with naked hands. Use rubber gloves..

Question 10.
Draw a battery of four cells?

Question 11.
How does electromagnetic induction find its use or application in generating electricity?
Answer:
The act of moving a magnet quickly in or cut of a coil of wire, can cause a current to flow in the wire. This phenomenon is called electromagnetic induction. This finds its application in generators where the coil is connected to a turbine. That rotates by the energy of falling water and moves the coil and causes current to flow, generators used in power stations have coil kept stationary and the magnet itself is rotated.

Question 12.
What forms the basic principle in electromagnets?
Answer:
Producing electromagnets is based on the principle that when current is passed through a coil it behaves like a magnet i.e., achieves north and south pole. Also if we reverse the direction of current in the coil the two poles exchange places. In electromagnets we insert a piece of iron in such a coil, its domain will get aligned in a direction normal to the face of the coil and the piece of iron gets strongly magnatised and act as electromagnets.

Electric Current and its Effects Long Answer Type Questions

Question 1.
Find the various ways in which two batteries and two bulbs can be connected in a working circuit?
Answer:
Two batteries and two bulbs can be connected in working circuit in two ways:
1. In series as shown in figure.

2. In parallel as shown in figure.

Question 2.
Give the symbols used for: open key; closed key, dry cell, a wire point, a battery and a bulb?
Answer:
The symbols are:

Question 3.
How can conductivity of a substance be tested?
Answer:
We can perform an experiment to test whether the given material conducts electricity or not. Make a circuit with wire, battery, bulb and connect them. If the bulb lights up, we can be sure that current is flowing in the circuit. Break the circuit. Now Fi8- TestinS whether a maternal close the circuit by inserting conducts electricity. different materials in between as (A) Match Stick (B) Pencil (C) Water (D) Eraser (E) Paper cup. Now see whether the bulb lights up. If it lights up, the material used for insertion in a conductor and if the bulb does not light up, the material is an insulator.

Question 4.
Define Miniature Circuit Breaker (MCB) with diagram?
Answer:
These day Miniature Circuit Breakers (MCBs) are increasingly being used in place of fuses. These are switches which automatically turn off when current in a circuit exceeds the safe limit. You turn them join and the circuit is once again complete. Look for ISI mark on MCBs also.

Question 5.
Define the working of an electric bell with circuit?
Answer:
We are quite familiar with an electric bell. It has an electromagnet in it. Fig. shows the circuit of an electric bell. It consists of a coil of wire wound on an iron piece. The coil acts as an electromagnet. An iron strip with a hammer at one end is kept close to the electromagnet.

There is a contact screw near the iron strip. When the iron strip is in contact with the screw, the current flows through the coil which becomes an electromagnet. It, then, pulls the iron strip. In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound. However, when the electromagnet pulls the iron strip, it also breaks the circuit. The current through the coil stops flowing.

The coil is no longer an electromagnet. It no longer attracts the iron strip. The iron strip comes back to its original position and touches the contact screw again. This completes the circuit. The current flows in the coil and the hammer strikes the gong again. This process is repeated in quick succession. The hammer strikes the gong every time the circuit is completed. This is how the bell rings.

MP Board Class 7th Science Solutions

MP Board Class 9th Science Solutions Chapter 8 Motion

Motion Intext Questions

Motion Intext Questions Page No. 100

Question 1.
An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Answer:
Yes, if an object start from a point and finally, reaches the same point. Then, it has distance but displacement is zero.

Question 2.
A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds?
Answer:

Suppose farmer starts from A of the square field.
Now, he covered 10 m in 40 sec.
Now, 2 minutes 20 seconds =140 sec.
So, he cover in 140 seconds = \(\frac { 10 }{ 40 }\) × 140 m
= \(\frac { 140 }{ 4 }\)m
= 35 m.
Now, in square field = 35m
AB + BC + CD + DE (\(\frac { 1 }{ 2 }\)AD)
So, he will reach at E.
Then, his displacement is AE = 5 m.

Question 3.
Which of the following is true for displacement?

1. It cannot be zero.
2. Its magnitude is greater than the distance travelled by the object.

Answer:

1. False
2. False.

Motion Intext Questions Page No. 102

Question 1.
Distinguish between speed and velocity.
Answer:

Question 2.
Under what condition (s) is magnitude of average velocity of an object equal to its average speed?
Answer:
When a body is moving in a straight line in a particular direction.

Question 3.
What does the odometer of an automobile measure?
Answer:
It measures the distance travelled by the vehicle.

Question 4.
What does the path of an object look like when it is in uniform motion?
Answer:
Straight line.

Question 5.
During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is 3 × 10⁸ m/s.
Answer:
Time taken by signal to reach ground station = 5 minutes
= 5 × 60 sec.
= 300 seconds.
Speed of the signal = 3 × 10⁸ m/s.
∴ Distance between spaceship and ground station = speed × time
= 3 × 10⁸ × 300
= 9 × 10¹⁰ m.

Motion Intext Questions Page No. 103

Question 1.
When will you say a body is in

1. Uniform acceleration?
2. Non – uniform acceleration?

Answer:

1. A body is in uniform acceleration if its velocity changes uniformly with equal intervals of time. Example: Freely falling object.
2. A body is in non – uniform acceleration if its velocity changes non – uniformly with equal intervals of time. Example: A bus running in a city.

Question 2.
A bus decreases its speed from 80 km/h^-1 to 60 km/h^-1 in 5 s. Find the acceleration of the bus.
Answer:
Initial velocity of the bus, u = 80 km/h
= \(\frac { 80\times 100 }{ 60\times 60 } \) m/s
u = \(\frac { 800 }{ 36} \) m/s
Final velocity of the bus, v = 60 km/h
= \(\frac { 60\times 100 }{ 60\times 60 } \) m/s
v = \(\frac { 600 }{ 36 } \) m/s
Time taken by bus to change its speeds, t = 5 seconds
∴ Acceleration, a = \(\frac { v-u }{ t } \)
= \(\frac { 600 }{ 36 } \) – \(\frac { 800 }{ 36 } \) ÷ 5
= \(\frac { 600-800 }{ 36 } \) ÷ 5
= \(\frac { 200 }{ 36 } \) × \(\frac { 1 }{ 5 } \) m/s²
= \(\frac { -10 }{ 9 } \) m/s²
a = -1.11 m/s².

Question 3.
A train starting from a railway station and moving with uniform acceleration attains a speed of 40 km/h^-1 in 10 minutes. Find its acceleration.
Answer:
Initial velocity, u = 0
Final velocity, v = 40 km/h
= \(\frac { 40\times 1000 }{ 60\times 60 } \) m/s
= \(\frac { 400 }{ 36 } \) m/s
= \(\frac { 200 }{ 18 } \) m/s.
Time taken, t = 10 minutes
= 10 × 10 seconds = 100 seconds
a = \(\frac { v-u }{ t } \)
= \(\frac { 200 }{ 18 } \) – 0 ÷ 100
= \(\frac { 200 }{ 18 } \) ÷ 100
= \(\frac { 200 }{ 18 } \) × \(\frac { 1 }{ 100 } \) m/s²
= \(\frac { 1 }{ 9 } \) m/s²
a = 0.018 m/s².

Motion Intext Questions Page No. 107

Question 1.
What is the nature of the distance – time graphs for uniform and non – uniform motion of an object?
Answer:
For uniform motion, it is a straight line.

For non – uniform motion, it is a curved line.

Question 2.
What can you say about the motion of an object whose distance – time graph is a straight line parallel to the time axis?
Answer:
It shows the body at rest.

Question 3.
What can you say about the motion of an object if its speed – time graph is a straight line parallel to the time axis?
Answer:
It means body has constant speed or uniform motion with zero acceleration.

Question 4.
What is the quantity which is measured by the area occupied below the velocity-time graph?
Answer:
Distance travelled.

Motion Intext Questions Page No. 109 – 110

Question 1.
A bus starting from rest moves with a uniform acceleration of 0.1 m/s² for 2 minutes. Find
(a) the speed acquired,
(b) the distance travelled.
Answer:
Initial velocity, u = 0
Acceleration, a = 0.1 m/s²
Time, t = 2 min = 2 × 60 seconds
= 120 seconds
(a) Velocity, v = ?
We know, v = u + at
v = 0 + 0.1 × 120 m/s
= 12 m/s.

(b) Distance, s = ?
We Know, s = ut + \(\frac { 1 }{ 2 }\) at²
= 0 × 120 + \(\frac { 1 }{ 2 }\) × 0.1 × 120 × 120
= \(\frac { 1 }{ 2 }\) × \(\frac { 0.1 }{ 10 }\) × 120 × 120 m
= 720 m.

Question 2.
A train is travelling at a speed of 90 km/h^-1. Brakes are applied so as to produce a uniform acceleration of – 0.5 m/s². Find how far the train wilt go before it is brought to rest.
Answer:
Initial velocity, u = 90 km/h
= \(\frac { 90\times 5 }{ 18 } \) m/s
= 25 m/s
Final velocity, v = 0
Acceleration, a = -0.5 m/s².
Distance, s = ?
We know,
v² = u² + 2as
0² = (25)² + 2 × (-0.5) × s
0 = 625 – 1 × s
= 625 – 1 × s
= 625 – s
∴ s = 625 m.
∴ Distance travelled by the train = 625 m.

Question 3.
A trolley while going down an inclined plane, has an acceleration of 2 cm/s². What will be its velocity in 3 s after the start?
Answer:
Acceleration, a = 2 cm/s²
Time, t = 3 sec.
Initial velocity, u = 0
Final velocity, v = ?
Now, v= u + at
v = 0 + 2 × 3
= 6 cm/s.

Question 4.
A racing car has a uniform acceleration of 4 m/s². What distance will it cover in 10 s after start?
Answer:
Acceleration, a = 4 m/s²
Time, t = 10 sec,
Initial velocity, u = 0
Distance, s = ?
Now, s = ut + \(\frac { 1 }{ 2 }\) at²
s = 0 × 10 + \(\frac { 1 }{ 2 }\) × 4 × (10)²
s = \(\frac { 1 }{ 2 }\) × 4 × 100 m
s = 200 m.
So, the distance covered is 200 m.

Question 5.
A stone is thrown in a vertically upward direction with a velocity of 5 m/s^-1. If the acceleration of the stone during its motion is 10 m/s^-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?
Answer:
Initial velocity, u = 5 m/s
Final velocity, v = 0
Acceleration, a = -10 m/s² (∴ It is from opposite direction)
Height attained, s = ?
Time taken, t = ?
Now, V² = u² + 2 as
(0)² = (5)² + 2 × (-10) × s
0 = 25 – 20s
⇒ 20s = 25
∴ s = \(\frac { 25 }{ 20 }\) = \(\frac { 5 }{ 4 }\) = 1025m
Now, v = u + at
0 = 5 + (-10) × t
0 = 5 – 10 × t
-5 = -10 × t
∴ t = \(\frac { -5 }{ -10 }\) = \(\frac { 1 }{ 2 }\) = 0.5 sec
So, height attained by the stone is 1.25 m and time taken to reach there is 0.5 sec.

Motion NCERT Textbook Exercises

Question 1.
An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?
Answer:

Diameter of the track = 200 m
So, radius = \(\frac { 200 }{ 2 }\) m
= 100m
Circumference = 2πr
= 2 × \(\frac { 22 }{ 7 }\) × 100 m
= \(\frac { 4400 }{ 7 }\) m.
Now, athlete covers 200 m in 40 s.
So, rounds covered in 40 seconds = 1
Rounds covered in 1 sec = \(\frac { 1 }{ 40 }\)
Rounds covered in 140 sec = \(\frac { 1 }{ 40 }\) × 140
= 3.5 rounds
So, distance covered = 3.5 × circumference
= \(\frac { 3.5 }{ 10 }\) × \(\frac { 4400 }{ 7 }\) m
= 2200 m.
And, displacement after 3.5 rounds
= Diameter of track
= 200 m.

Question 2.
Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging (a) from A to B and (b) from A to C?
Answer:

(a) A to B,
Time taken, t = 2 min, 30 sec
= 150 sec.

= \(\frac { 300 }{ 150 }\) m/s = 2 m/s

= \(\frac { 300 }{ 150 }\) m/s = 2 m/s.

(b) A to C,
Time taken = Time from A to B + Time from B to C
= 2 min 30 sec + 1 min
= 150 sec + 60 sec
= 210 sec.
Total distance covered (AB + BC) = (300 + 100) m
= 400 m
Displacement = AC = (300 – 100) m
= 200 m

= \(\frac { 400 }{ 210 }\) m/s = 1.9 m/s

= \(\frac { 200 }{ 210 }\) m/s = 0.95 m/s.

Question 3.
Abdul, while driving to school, computes the average speed for his trip to be 20 kmh^-1. On his return trip along the same route, there is less traffic and the average speed is 30 kmh^-1. What is the average speed for Abdul’s trip?
Answer:
Let the distance between Abdul’s home and school = x km.
Lets time taken from home to school = t₁ hr.
and time taken from school to home = t₂ hr.
Now,

∴ t₁ = \(\frac { x }{ 20 }\) hr.
t₂ = \(\frac { x }{ 30 }\) hr.
Now,

∴ Average Speed = \(\frac { 120 }{ 5 }\) 24 km/h.

Question 4.
A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 3.0 ms^-2 for 8.0 s. How far does the boat travel during this time?
Answer:
Initial velocity, u = 0
Acceleration, a = 3.0 m/s²
= 3 m/s²
Time, t = 8 sec
Now,
s = ut + \(\frac { 1 }{ 2 }\) at²
s = 0 × 8 + \(\frac { 1 }{ 2 }\) × 3 × (8)²
= 0 + \(\frac { 1 }{ 2 }\) × 3 × 64
s = 96 m.
∴ Distance Travelled by Boat is 96 m.

Question 5.
A driver of a car travelling at 52 kmh^-1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 34 kmh^-1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?

Answer:
We have,
Speed of first driver = 52 km/h
= \(\frac { 52\times 1000 }{ 60\times 60 } \) m/s = 14.4 m/s
Speed of second driver = 3 km/h
= \(\frac { 3\times 1000 }{ 60\times 60 } \) m/s = 0.83 m/s
Now, distance covered by first driver = Area of ΔAOB
= \(\frac { 1 }{ 2 }\) × OA × OB
= \(\frac { 1 }{ 2 }\) × 14.4 × 5 = 36.1 m
Distance covered by second driver = Area of ΔMON
= \(\frac { 1 }{ 2 }\) × OM × ON
= \(\frac { 1 }{ 2 }\) × O.83 × 10 = 4.16 m
So, first driver covers more distance.

Question 6.
Figure below shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions:

1. Which of the three is travelling the fastest?
2. Are all three ever at the same point on the road?
3. How far has C travelled when B passes A?
4. How far has B travelled by the time it passes C?

Answer:

1. B is travelling the fastest.
2. No.
3. C was at around 9 km from origin when B passes A.
4. B travelled around 5.5 km when it passes C.

Question 7.
A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 ms^-2, with what velocity will it strike the ground? After what time will it strike the ground?
Answer:
Distance, s = 20 m
Initial velocity, u = 0
Acceleration, a = 10 m/s²
Now, s = ut +\(\frac { 1 }{ 2 }\) at²
20 = 0 × t + \(\frac { 1 }{ 2 }\) × 10 × t²
20 = 5 × t²
∴ t² = \(\frac { 20 }{ 5 }\) = 4
∴ t = 2 sec.
Also, v = u + at
v = 0 + 10 × 2
y = 20 m/s.
So, it will strike the ground after 2 seconds with the velocity of 20 m/s.

Question 8.
The speed – time graph for a car is shown in figure below:

(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
(b) Which part of the graph represents uniform motion of the car?
Answer:
(a) The distance travelled by car in first 4 seconds
= Area of triangular like region OAB
= \(\frac { 1 }{ 2 }\) × AB × OB = \(\frac { 1 }{ 2 }\) × 6.9 × 4
= 12 m (approximately).

(b) Part of the graph after 5.5 seconds shows the uniform motion.

Question 9.
State which of the following situations are possible and give an example for each of these:

1. an object with a constant acceleration but with zero velocity.
2. an object moving in a certain direction with an acceleration in the perpendicular direction. Both are possible.

Answer:

1. Freely falling.
2. Motion of an object in a circular path.

Question 10.
An artificial, satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.
Answer:
Radius of the orbit = 42250 km = 42250 × 1000 m.
Time taken to complete one revolution = 24 hours.
= 24 × 60 × 60 sec
Distance covered by satellite to complete 1 revolution = 2πr
= 2 × \(\frac { 22 }{ 7 }\) × 42250 × 1000 m

Motion Additional Questions

Motion Multiple Choice Questions

Question 1.
Deceleration of a body is expressed in _______ .
(a) m
(b) ms^-1
(c) ms^-2
(d) -ms^-2
Answer:
(c) ms^-2.

Question 2. A car goes from town A to another town B with a speed of 40 km/h and returns back to the town A with a speed of 60 km/h. The average speed of the car during the complete journey is _______ .
(a) 48 km/h
(b) 50 km/h
(c) Zero
(d) None of these.
Answer:
(a) 48 km/h

Question 3.
A ball is thrown vertically upwards. It rises to a height of 50 m and comes back to the thrower, _______ .
(a) The total distance covered by the ball is zero.
(b) The net displacement of the ball is zero.
(c) The displacement is 100 m.
(d) None of the above.
Answer:
(b) The net displacement of the ball is zero.

Question 4.
The SI unit of velocity is _______ .
(a) ms^-1
(b) ms^-2
(c) ms^-3
(d) Nm^-1.
Answer:
(a) ms^-1

Question 5.
In 12 minutes a car whose speed is 35 km/h travels a distance of _______ .
(a) 7 km
(b) 3.5 km
(c) 14 km
(d) 28 km.
Answer:
(a) 7 km

Question 6.
A 50 m long train passes over a 250 m long bridge at a velocity of 60 km/h. How long will it take to pass completely over the bridge?
(a) 18 s
(b) 20 s
(c) 24 s
(d) none of these.
Answer:
(a) 18 s

Question 7.
The initial velocity of a train which is stopped in 20 s by applying brakes (retardation due to brakes being 1.5 ms^-2) is _______ .
(a) 30 ms^-1
(b) 30 cm^-1
(c) 20 cm^-1
(d) 24 ms^-1.
Answer:
(a) 30 ms^-1

Question 8.
A wooden slab starting from rest, slides down a 10 m long inclined plane with an acceleration of 5 ms². What would be its speed at the bottom of the inclined plane?
(a) 10 ms^-1
(b) 12 ms^-1
(c) 10 cm s^-1
(d) 12 cm s^-1.
Answer:
(a) 10 ms^-1

Question 9.
m/s² is the SI unit of _______ .
(a) Distance
(b) Displacement
(c) Velocity
(d) Acceleration.
Answer:
(d) Acceleration.

Question 10.
A car increases its speed from 20 km/h to 50 km/h in 10 seconds. Its acceleration is _______ .
(a) 30 m/s²
(b) 3 m/s²
(c) 18 m/s²
(d) 0.83 m/s².
Answer:
(d) 0.83 m/s².

Motion Very Short Answer type Questions

Question 1.
Define uniform motion.
Answer:
When an object covers equal distances in equal intervals of time: it is said to be in uniform motion.

Question 2.
Define speed.
Answer:
It is defined as the distance travelled by an object in unit time. Its unit is m/s.

Question 3.
Define average speed.
Answer:
The total distance travelled by an object divided by the total time taken.

Question 4.
Define velocity.
Answer:
Velocity is the speed of an object moving in definite direction.

Question 5.
Define acceleration.
Answer:
Change in the velocity of an object per unit time.
a = \(\frac { v-u }{ t } \), S.I. unit is m/s².

Motion Short Answer type Questions

Question 1.
While plotting a distance – time graph, why do we plot time on x – axis.
Answer:
While plotting a distance – time graph, we should plot time on x – axis as, all independent quantities are plotted on x – axis.

Question 2.
What is odometer?
Answer:
Odometer is a device fitted in the automobiles to show the distance travelled.

Question 3.
Draw a distance – time graph that represents uniform speed.
Answer:

Question 4.
With the help of distance – time graph show that the object is stationary.
Answer:

Question 5.
What does the area under velocity – time graph represent?
Answer:
The area under the velocity – time graph represents the displacement.

Question 6.
A body travels a distance from A to B, its physical quantity is measured to be -15 m/s. Is it speed or velocity? Give reason for the answer.
Answer:
The physical quantity is -15 m/s. It represents velocity because sign of speed cannot be a negative. Negative sign indicates the opposite direction.

Question 7.
What type of velocity – time graph will you get for a particle moving with a constant acceleration?
Answer:
For a particle moving with a constant acceleration velocity – time graph will be a straight line inclined to x – axis.

Question 8.
Define uniform circular motion.
Answer:
When a body moves in a circular path with uniform speed, its motion is called uniform circular motion.

Question 9.
What is deceleration?
Answer:
When the speed of an object decreases, the object is said to be decelerating. In this case, the direction of acceleration is opposite to the velocity of the object.

Question 10.
What conclusion do you draw about acceleration of the particle in motion from given velocity – time graphs?

Answer:
(a) No acceleration.
(b) Uniform acceleration.
(c) Non – uniform acceleration.

Question 11.
With the help of graph, show the uniform acceleration and uniform retardation of a body.
Answer:

• OA – Shows uniform acceleration.
• CB – Shows uniform retardation.

Question 12.
Give difference between acceleration and velocity.
Answer:
table

Motion Long Answer Type Questions

Question 1.
How can we get speed from distance – time graph?
Answer:
Let us assume that an object moves with a uniform speed. The distance – time graph will be a straight line.
Let d₁ be the distance covered in time t₁.
Let d₂ be the distance covered in time t₂.
∴ d₂ – d₁ will be the distance covered in t₂ – t₂.

But, here \(\frac { BC }{ AC }\) = slope of the graph.
Conclusion:
To find the speed from distance – time graph, we can get its slope which is equal to the speed of the object.

Question 2.
Represent a graph that shows the following:
(a) Uniform speed
(b) Non – uniform speed
(c) Stationary object.
Answer:
Time is taken on x – axis as it is independent quantity and all dependent quantities are taken along y – axis.

Question 3.
(a) What is motion?
(b) State types of motion.
(c) Derive the unit for acceleration.
Answer:
(a) Motion: An object is said to be in motion when its position changes with time. We describe the location of an object by specifying a reference point. Motion is relative. The total path covered by an object is said to be the distance travelled by it.

(b) There are two types of motion: Uniform motion and non – uniform motion

• Uniform motion: When an object covers equal distances in equal intervals of time, it is said to be in uniform motion.
• Non – uniform motion: Motion where object cover unequal distances in equal intervals of time.

(c) Acceleration, ‘a’ is change in velocity per unit time.

Question 4.
(a) What is uniform circular motion?
(b) An athlete runs on a circular track, whose radius is 50 m with a constant speed. It takes 50 seconds to reach point B from starting point A. Find:

1. the distance covered.
2. the displacement.
3. the speed.

Answer:
(a) When a body moves in a circular path with uniform speed, its motion is called uniform circular motion.

(b) Radius = 50 m
Time = 50 s
The distance covered by an athlete A to B i.e., semicircle of the track
∴ Circumference = 2πr
circumference half of = πr.

Question 5.
Derive the equation for velocity – time relation (v = u + at) by graphical method.
Answer:

Let, the initial velocity of a body be, u = OA = CD.
The final velocity of a body be, v = OE = CB
Time, t = OC = AD
AD is parallel to OC
BC = BD + DC
= BD + OA
v = BD + u
∴ BD =v – u …….. (1)
In velocity – time graph, slope gives acceleration.
∴ a = \(\frac { BD }{ AD }\) = \(\frac { BD }{ OC }\) = OC = t
we get, a = \(\frac { BD }{ t }\)
∴ BD = at …….. (2).

Question 6.
A car accelerates uniformly from 20 km/h to 35 km/h in 5 s. Calculate (i) the acceleration and (ii) the distance covered by the car in that time.
Answer:
u =20 km/h = 5.5 m/s
v =35 km/h = 9.72 m/s
t = 5 s
a = \(\frac { v-u }{ t } \)
= \(\frac { 9.7-5.5 }{ 5 } \)
a = \(\frac { 4.2 }{ 5 } \)
= 0.84 m/s².

(ii) The distance covered by the car s = ut + \(\frac { 1 }{ 2 }\) at²
= 5.5 × 5 + \(\frac { 1 }{ 2 }\)(0.84)(5)²
= 27.5 + \(\frac { 1 }{ 2 }\) × 0.84 × 25
= 27.5 + 10.5
s = 38 m.

Question 7.
Draw graph to show the following:
(a) Uniform acceleration.
(b) Non – uniform acceleration.
(c) Uniform motion.
Answer:

Uniform acceleration – A body travels equal distances in equal intervals of time.

Non – uniform acceleration – A body travels unequal distances in equal intervals of time.

Uniform motion or zero acceleration A body moves with constant speed in same line.

Question 8.
How can you get the distance travelled by an object from its speed – time graph?
Answer:

Suppose an object is moving with a same speed v, the distance covered by this object when it was at (point A) t₁ to t₂ is:
AB = t₂ – t₁
AD = BC = v

= AD . AB
∴ s = Area of rectangle ABCD
∴ To find the distance travelled by a body from its speed – time graph, we need to find the area enclosed by the graph.

Motion Higher Order Thinking Skills (HOTS)

Question 1.
A blacksmith strikes a nail with a hammer of mass 500 g moving with a velocity of 20 ms^-1. The hammer comes to rest in 0.02 s after striking the nail. Calculate the force exerted by the nail on the hammer.
Answer:
m = 500 g = \(\frac { 1 }{ 2 }\) kg
u = 20 ms^-1 , v = 0
t = 0.02 s, F = ?

Therefore, force exerted by nail on the hammer = 500 N.

Motion Value Based Question

Question 1.
A jeep was moving at a speed of 120 km/h on an highway. All of a sudden tyre of the jeep got punctured and burst The driver of the jeep did not apply sudden brakes but he slowed down its speed and finally stopped it at the road side. All the passengers in the jeep were shocked but happy with the driver’s decison.

1. What would have happened if the driver applied sudden brakes?
2. On applying brakes in which direction would the passengers fall?
3. What value of driver is reflected in this act?

Answer:

1. If the driver would have applied sudden brakes, then all the passengers would get hurt and even other vehicles moving on the highway would have collided with this jeep from behind.
2. On applying brake, the passengers would fall in the forward direction.
3. The driver showed the presence of mind, concern and responsible behaviour and quick decision taking capability.

MP Board Class 9th Science Solutions