NCERT Solutions for Class 8 Science Chapter 11 – Force and Pressure, contains solutions to various questions in Exercise for Chapter 11. At the end of the Solutions, all the keywords and Notes which are important to understand Science Chapter 11 – Force and Pressure, have been explained in a simple and easy-to-understand manner. NCERT Solutions for Class 8 help to check the concept you have learned from detailed classroom sessions and the application of your knowledge.
| Category | NCERT Solutions for Class 8 |
| Subject | Science |
| Chapter | Chapter 11 – Force and Pressure |
Download NCERT Solutions for Class 8 Science Chapter 11 – Force and Pressure
NCERT Solutions for Class 8 Science Chapter 11 – Force and Pressure– NCERT Exercises
Question1
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Answer 1.
Examples of pushing:
- Pushing a heavy block to displace it from its original position
- Putting your weight against a couch to move it
- Pushing a trolley
Examples of pulling:
- Pulling the rope of a pulley to draw water from a well
- Pulling back the string of a bow to shoot an arrow
Question 2
Give two examples of situations in which applied force causes a change in the shape of an object.
Answer 2.
Two examples of situations in which applied force causes a change in the shape of an object are:
- Pressing of dough on a plate to change its shape to a required form
- Sitting on the seat of a bicycle compresses the spring under it
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 3.
(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 pull it.
(d) The north pole of a magnet repels the north pole of another magnet.
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 4.
(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 of 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.
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 5.
| Agents Exerting the Force | Objects on which force is exerted | Effect of the force |
|---|---|---|
| (a) Fingers | Lemon | Extraction of the lemon juice |
| (b) Fingers | Toothpaste tube | Toothpaste comes out |
| (c) A load | Spring | Spring expands |
| (d) An athlete | On the Legs | Jumping to clear the bar |
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 6.
The force exerted due to hammering on the hot piece of iron allows the blacksmith to change the shape of the iron piece and mould it into any desired 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 7.
When the balloon is rubbed with a synthetic cloth then it gets charged due to friction. When it is pressed against a wall then it sticks to the surface of the wall due to the electrostatic forces acting 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 8.
The forces acting on the plastic bucket containing water held above are:
- Gravitational forces
- Muscular forces
The forces acting on the bucket do not change its state of motion because the net pressure acting on the walls of the bucket by the water is zero and the gravitation force acting in the downward direction is balance by the equal and opposite force exerted by our hands in holding the bucket. Since the forces are equal in magnitude but opposite in direction so net force acting is again zero. As a result, 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 9. The two forces acting on the rocket immediately after leaving the launching pad are:
(i)Gravitational force
(ii)Frictional force due to the surrounding air
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 10.
(d)Atmospheric pressure
Topics Covered in Chapter 11 Force and Pressure Class 8 Science :-
- Force – A Push or a Pull
- Forces are due to an Interaction
- Exploring Forces
- A Force can Change the State of Motion
- Force can Change the Shape of an Object
- Contact Forces
- Non-contact Forces
- Pressure
- Pressure exerted by Liquids and Gases
- Atmospheric Pressure
Important Terms Relevant to understand NCERT Solutions for Class 8 Science Chapter 11 – Force and Pressure :-
Force: It is an external agent that is capable of changing the state of rest or the state of motion of an object. It is any form of push or pull on an object capable of changing its velocity.
State of motion: The state of motion of an object is defined by velocity- its speed and direction of motion.
State of rest: The state of rest is also a state of motion of zero velocity. An object is said to be at rest if its relative velocity is zero with respect to a particular frame of reference.
Contact Forces: These are the forces involved when two surfaces or bodies are in physical contact with each other such as tension, friction, spring force, normal reaction etc.
Non-Contact Forces: These are the forces which act between two or more bodies without any physical contact in between them such as gravitational force, electrostatic force etc.
Muscular Force: The force resulting due to the action of muscles is known as muscular force. It is also a contact force.
Pressure: It is the normal force or thrust acting on an object per unit area of a surface.
Atmosphere: It is layer or a set of layers of gases that is set in place under the influence of the gravity of a body.
Atmospheric pressure: It is the force exerted per unit area by a column of atmospheric air. It is also known as barometric pressure and has a standard value of 101,235 pascals.
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