NCERT Solutions for Class 8 Science Chapter 11 Force and Pressure

This chapter of NCERT solutions for class 8 science explains force and the different types of forces present in our world. Some of the important ones include Frictional force, Gravitational force, magnetic force, electrostatic force etc. Students will also understand the difference between push and pull and pressure.

When we enter a shop, we always see the notice- Push and Pull on the door. So to enter, we pull the door outwards and to exit we push the door again outwards. Or we can push the door inwards as well to enter.

This pressure that we apply to the door is force and it is applied with a certain amount of strength and in a particular direction. So, we say Force has magnitude and direction.

Download PDF of NCERT Solutions for Class 8 Science Chapter 11

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

Answer:

Examples of Push

i. Pushing a heavy bag across the floor

ii. Closing a window

Examples of Pull

i. Opening a window

ii. Pulling a book lying on the table

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

Answer:

i. Squeezing an empty tin

ii. Stretching an elastic band

Question 3. Fill in the blanks in the following statements.

(a) To draw water from a well we have to __________ at the rope.

Answer:

To get water from the well, we pull the ropes.

(b) A charged body __________ an uncharged body towards it.

Answer:

A charged body will attract another charged or uncharged body.

(c) To move a loaded trolley we have to __________ it.

Answer:

We push a loaded trolley to make it move.

(d) The north pole of a magnet _______________ the north pole of another magnet.

Answer:

The north poles of magnets repel each other.

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 force, gravity, friction, shape, attraction

(a) To stretch the bow, the archer applies a force that causes a change in its __________.

Answer:

The shape of the bow changes when the archer stretches it.

(b) The force applied by the archer to stretch the bow is an example of __________ force.

Answer:

The archer uses muscular force to stretch the bow.

(c) The type of force responsible for a change in the state of motion of the arrow is an example of a __________ force.

Answer:

A contact force changes the arrow’s state of motion.

(d) While the arrow moves towards its target, the forces acting on it are due to __________ and that due to __________ of air.

Answer:

The two forces acting on the arrow will be gravity and friction due to air.

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.

Answer:

Agent - Fingers

Object - Lemon

Effect of force - Shape of the lemon changes

(b) Taking out paste from a toothpaste tube.

Answer:

Agent - Fingers

Object - Toothpaste

Effect of force - Shape of toothpaste tube changes

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

Answer:

Agent - Load

Object - Spring

Effect of force - Shape of spring changes

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

Answer:

Agent - Athlete

Object - Ground

Effect of force - Change in athlete’s state of motion

Also get access to

NCERT Solutions for Class 8 Maths

Class 8 Maths Worksheets

Class 8 Maths Notes

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:

When a blacksmith hammers a hot piece of iron, it changes shape.

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:

When the inflated balloon is rubbed against a piece of cloth, it becomes charged. The electrostatic force between the balloon and the wall causes it to stick to 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:

To keep the water-filled bucket above ground level, we use muscular force in the upward direction. The force of gravity also acts on it in a downward direction. Both forces are equal and act in opposite directions. As a result, the bucket's state of motion remains unchanged.

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:

Friction due to air and force of gravity are the two forces acting on the rocket immediately after the launch.

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:

When the pressure on the dropper is released, the atmospheric pressure acting on the water causes it to rise in the dropper.

Links to Other Resources for Class 8 Science

Other Class 8 Science Related Links
Understanding Structure and Functions of a Cell
Deforestation, Afforestation and Reforestation
Frictional Force Definition, and Types with Example
Compare LPG and Wood as Fuel
Water Pollution Causes and Effects with Example