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Force and Pressure Chapter 11 Class 8 NCERT solutions


NCERT Solutions

In this page we have Force and Pressure Chapter 11 Class 8 NCERT solutions . Hope you like them and do not forget to like , social shar and comment at the end of the page.

Question 1

Give two examples each of situations in which you push or pull to change the state of motion of objects.

Answer

Two examples of push force are as follows:
1) A big box at rest is pushed to move it from one place to another. This changes the state of motion of the box.
2) A player pushes a ball using his hockey stick. This changes the state of motion of the ball.

Two examples of pull force are as follows:
1) Rope is pulled to draw water from a well. This changes the state of motion of the water bucket.
2) A suitcase is pulled from alimirah

Question 2

Give two examples of situations in which applied force causes a change in the shape of an object.

Answer

1) Making of bread from dough
2) Hammer hitting on red hot iron.

Question 3

Fill in the blanks in the following statements.
(a) To draw water from a well we have to _________at the rope.
(b) A charged body ________an uncharged body towards it.
(c) To move a loaded trolley we have to _________it.
(d) The north pole of a magnet ________the north pole of another magnet.

Answer

(a) pull
(b) attracts
(c) push or pull
(d) repels


Question 4

An archer stretches her bow while taking aim at the target. She then releases the arrow, which begins to move towards the target. Based on this information fill up the gaps in the following statements using the following terms.

muscular, contact, non-contact, gravity, friction, shape, attraction

(a) To stretch the bow, the archer applies a force that causes a change in its _______.
(b) The force applied by the archer to stretch the bow is an example of ________force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example of a_______ force.
(d) While the arrow moves towards its target, the forces acting on it are due to ________and that due to ________of air.


Answer

(a) shape.

(b) muscular
(c) contact
(d) gravity, friction

Question 5

In the following situations identify the agent exerting the force and the object on which it acts. State the effect of the force in each case.


(a) Squeezing a piece of lemon between the fingers to extract its juice.

(b) Taking out paste from a toothpaste tube.

(c) A load suspended from a spring while its other end is on a hook fixed to a wall.

(d) An athlete making a high jump to clear the bar at a certain height.

Answer

S.no

Situation

Agent exerting the force

Object on which force acts

Effect of force

a)

Squeezing a piece of lemon between the fingers to extract its juice

Fingers

Lemon

Change in shape of lemon

b)

Taking out paste from a toothpaste tube.


Fingers

 toothpaste tube

Change in shape of toothpaste tube

c)

A load suspended from a spring while its other end is on a hook fixed to a wall.


Load

Spring

Change in shape of spring

d)

An athlete making a high jump to clear the bar at a certain height.

Muscles of Athlete

Athlete

Change of state of motion of athlete


Question 6

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammering affect the piece of iron?

Answer

The force due to hammering changes the shape of the piece of iron


Question 7. 

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

Answer

Electrostatic force is responsible for the attraction between the balloon and the wall.

Question 8

Name the forces acting on a plastic bucket containing water held above ground level in your hand. Discuss why the forces acting on the bucket do not bring a change in its state of motion.

Answer

There are two forces acting on plastic bucket

a) Muscular force is acting in upward direction

b) The force of gravity is acting in downward direction.

Now Both forces are acting in opposite directions to each other and hence cancel the effect of each other. Due to this, there is no change in the state of motion of the bucket.

Question 9

A rocket has been fired upwards to launch a satellite in its orbit. Name the two forces acting on the rocket immediately after leaving the launching pad.

Answer

The two forces acting on the rocket are given below

1)  The force of gravity, which pulls the rocket towards the ground

2) The force of friction due to earth's atmosphere, which opposes its motion.

Question 10

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
(a) pressure of water.
(b) gravity of the earth.
(c) shape of rubber bulb
(d) atmospheric pressure

Answer

(d) atmospheric pressure

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