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# NCERT Solutions for Class 8 Science Chapter 11 : Force and Pressure

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NCERT solutions for Class 8 Science chapter 11 is Force and Pressure. It is provided here to help students to follow the concepts in an easy way. Answers provided here will help you to get the knowledge on the concept of Force, magnitude and direction of force, change in its state of motion or a change in its shape, definition of pressure, the exertion of pressure on liquid and gases.

NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure by Swiflearn are by far the best and most reliable NCERT Solutions that you can find on the internet. These NCERT Solutions for Class 8 Science Chapter 11 are designed as per the CBSE Class 8 Science Syllabus. These NCERT Solutions will surely make your learning convenient & fun. Students can also Download FREE PDF of NCERT Solutions Class 8 Chapter 11 Force and Pressure.

## NCERT Solutions for Class 8 Science Chapter 11 : Force and Pressure

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

Solution:
Two examples of situations where push is used to change the state of motion of the objects:
1. A heavy trolley at rest is pushed to move it from one place to another. This changes the state of motion of the trolley.
2. Acarom coin is pushed by the striker. This changes the state of motion of the coin.
Two examples of situations where pull is used to change the state of motion of the objects:
1. Pulling the rope to draw water from a well. This changes the state of motion of the water bucket.
2. A cart is pulled to move it from one place to other. This changes the state of motion of the cart.

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

Solution:
Two examples of situations where the applied force causes a change in the shape of an object are as follows:
 squeezing an empty plastic bottle with hands

#### 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.

Solution:
(a) To draw water from a well we have to pull at the rope.
(b) A charged body attracts an uncharged body towards it.
(c) To move a loaded trolley we have to push it.
(d) The north pole of a magnet repels the north pole of another magnet.

#### (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.

Solution:
(a) To stretch the bow, the archer applies a force that causes a change in its shape.
(b) The force applied by the archer to stretch the bow is an example of muscular force.
(c) The type of force responsible for a change in the state of motion of the arrow is an example a contact force.
(d) While the arrow moves towards its target, the forces acting on it are due to gravity and that due to friction of air.

#### 5. In the following situations identify the agent exerting the force and the objecton 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.

Solution:
(a) Squeezing a piece of lemon between the fingers to extract its juice.
 Agent exerting the force – Fingers
 Object on which the force acts – Lemon
 Effect of force – Change in shape of the lemon

(b) Taking out paste from a toothpaste tube.
 Agent exerting the force – Fingers
 Object on which the force acts – Toothpaste tube
 Effect of force – Change in shape of the toothpaste tube

(c) A load suspended from a spring while its other end is on a hook fixed to a wall.
 Agent exerting the force – The load suspended from the spring
 Object on which the force acts – Spring
 Effect of force – Change in shape of the spring

(d) An athlete making a high jump to clear the bar at a certain height.
 Agent exerting the force – Muscles of the athlete
 Object on which force acts – The athlete
 Effect of the force – Change of state of motion of the athlete

#### 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?

Solution:
A blacksmith uses the muscular force when he hammers a hot piece of iron. As a result of this muscular force, the shape of the iron piece changes.

#### 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?

Solution:
The inflated balloon gets charged when it is rubbed with a piece of synthetic cloth. Due to the electrostatic force of attraction between the charged balloon and the uncharged wall, the balloon sticks to the wall.

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

Solution:
Muscular force and gravitational forces are acting on a plastic bucket. The forces acting on the bucket do not change the state of motion of the bucket because the two forces are acting in the opposite directions. The muscular force is acting in upward direction and the gravitational force is acting in the downward direction. Due to this, there is no change in the state of motion of the bucket.

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

Solution:
The two forces acting on the rocket immediately after leaving the launch pad are the force of gravity and the force of friction due to earth’s atmosphere.

#### 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.

Solution:
Atmospheric pressure is responsible for the rise of water in the dropper. This happens because when the bulb of the dropper is pressed, the air inside the dropper escapes, thereby reducing the air pressure inside the dropper. The atmospheric pressure outside the dropper is more and thus water is
sucked inside the dropper.