NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure

NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure helps you in getting good grades by providing solutions for all chapters that are related to the test. The solutions are also very detailed, giving students a better understanding of the concepts.

Chapter 11 CBSE Class 8 Science NCERT Solutions are very much essential in steering students towards their goal. It can be used for any purpose and are great for research and preparation for exams.

Chapter 11 Force and Pressure Class 8 Science NCERT Solutions

Exercises

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

Solution

(i) Pushing a shopping cart
(ii) Pulling open a heavy door

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

Solution

(i) Bending metal which can done by applying pressure to the metal, usually with a hammer or other tool
(ii) Pressing a lump of dough on a plate.

3. Fill in the blanks in the following statements.
(a) To draw water from a well we have to _______ 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) Pull
(b) Attracts
(c) Push or pull
(d) Repels

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 these 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.

Solution

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

5. In the following situations, identify the agent exerting the force and the object on which it acts. State the effect of force in each case.
(a) Squeezing a piece of lemon between your fingers to extract its juice
(b) Taking out toothpaste from its 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

Situation	Agent exerting force	Object on which force acts	Result
(a)	Fingers	Piece of lemon	Juice squeezes out
(b)	Fingers	Toothpaste tube	Toothpaste comes out
(c)	Suspended load	Spring	Spring elongates
(d)	Muscular force of legs	Athlete’s body	Athlete makes a high jump

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

The force applied by the hammer flattens the piece of iron, i.e., it changes its shape and size.

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

Solution

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

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?

Solution

We are lifting it with our hand, so muscular force acts upwards, and gravitational force acts downwards. There is no change in the state of motion of a bucket despite these forces acting on it, since they balance each other and there is no net force acting on it.

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.

Solution

(i) Gravitational force of the Earth which pulls rocket towards the ground.
(ii) Frictional force due to the Earth’s atmosphere which opposes its motion.

10. When we press the bulb of a dropper with its nozzle 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

(d) Atmospheric pressure