CBSE Class 8 Science Chapter 11: Force and Pressure NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

CBSE Class 8 Science Chapter 11 introduces the essential concepts of force and pressure. This chapter explores how forces influence the motion and shape of objects. Students will learn about various types of forces, including muscular force, contact forces, and non-contact forces like magnetic and gravitational forces. The solutions explain the effects of these forces, such as attraction and repulsion, and the role of friction in everyday life. Understanding these principles is vital for comprehending numerous physical phenomena and forms the basis for further studies in physics. The NCERT Solutions provide clear explanations and examples to help students grasp these fundamental ideas, ensuring a solid understanding for academic success.

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BoardCBSE
ClassClass 8
SubjectScience
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 11

Chapter summary

Chapter 11 of the Class 8 Science NCERT Solutions focuses on the concept of force and its effects. It explains how forces, whether pushes or pulls, can alter an object's motion or shape. The chapter introduces various types of forces, including contact forces (like muscular and friction) and non-contact forces (like magnetic and gravitational forces). It also touches upon the pressure exerted by forces. The exercises provide practical examples to reinforce these ideas, making it easier for students to understand the applications of force in everyday life.

Learning outcomes

  • Understand that force is a push or a pull that can change the state of motion or shape of an object.
  • Identify examples of pushing and pulling forces in everyday situations.
  • Differentiate between contact and non-contact forces.
  • Recognize the effects of forces, such as changing shape, speed, or direction.
  • Explain the role of muscular, gravitational, magnetic, and frictional forces.
  • Provide examples of forces causing changes in the shape of objects.

Topics covered

Paper topics

  • Force as push or pull
  • Examples of push and pull
  • Change in state of motion
  • Change in shape of objects
  • Contact forces
  • Muscular force
  • Non-contact forces
  • Magnetic force
  • Electrostatic force
  • Gravitational force
  • Friction
  • Pressure

Important topics

  • Force as a push or pull
  • Effects of force (change in motion/shape)
  • Contact vs. Non-contact forces
  • Examples of different forces (muscular, gravity, friction, magnetic)

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Questions and Solutions

Question 1

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

Forces are often described as pushes or pulls. These actions can cause an object to start moving, stop moving, move faster, move slower, or change its direction of motion. Here are two examples for each:

Examples of Pushing to change state of motion:

  1. Kicking a football: When you kick a stationary football, you apply a pushing force that causes it to move.
  2. Pushing a swing: To make a stationary swing start moving, you push it.

Examples of Pulling to change state of motion:

  1. Drawing water from a well: You pull the rope attached to the bucket to lift water upwards, changing its state of motion from rest to moving.
  2. Opening a drawer: You pull the handle of a drawer to open it, causing it to move towards you.

Question 2

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

Besides changing the state of motion, forces can also cause objects to change their shape. This means the object can be stretched, squeezed, bent, or flattened. Here are two examples:

  1. Stretching a rubber band: When you pull the ends of a rubber band, you apply a force that stretches it, changing its shape from a shorter, thicker form to a longer, thinner one.
  2. Reshaping clay to make toys: When you mould clay into different shapes to create toys, you are applying forces that deform the clay, changing its original shape into a new one.

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.

Solution:

Let's fill in the blanks with the appropriate terms based on our understanding of forces:

(a) To draw water from a well we have to pull at the rope. This is because we need to exert a force to lift the bucket against gravity.

(b) A charged body attracts an uncharged body towards it. This is an example of an electrostatic force, which can occur without direct contact.

(c) To move a loaded trolley we have to push it. Pushing is a force applied away from the body, which is necessary to set the trolley in motion.

(d) The north pole of a magnet repels the north pole of another magnet. Like poles of magnets always push each other away.

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.

Solution:

Let's analyze the archer's action and the arrow's flight to fill in the blanks:

(a) To stretch the bow, the archer applies a force that causes a change in its shape. The bow deforms from its original shape when stretched.

(b) The force applied by the archer to stretch the bow is an example of contact force. This is because the archer's hands are in direct physical contact with the bow to stretch it.

(c) The type of force responsible for a change in the state of motion of the arrow is an example of a muscular force. The archer uses her muscles to apply the force that propels the arrow.

(d) While the arrow moves towards its target, the forces acting on it are due to gravity (pulling the arrow downwards towards the Earth) and that due to friction of air (opposing the arrow's motion through the 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.

Solution:

Let's identify the agent, object, and effect of the force for each situation:

S. No. Object Agent Effect of the force
(a) Lemon Fingers The force applied by the fingers squeezes the lemon, changing its shape and causing the juice to be extracted.
(b) Toothpaste tube Fingers The force applied by the fingers squeezes the tube, changing its shape and forcing the toothpaste out.
(c) Spring Load The suspended load exerts a downward force on the spring, causing it to stretch or extend.
(d) Athlete's body Athlete's legs (pushing against the ground) The force exerted by the athlete's legs on the ground results in an upward force that propels the athlete's body upwards, allowing them to jump over the bar.

Common mistakes

  • Confusing push and pull actions.
  • Not distinguishing between contact and non-contact forces.
  • Misidentifying the agent applying the force or the object experiencing it.
  • Failing to recognize that forces can cause changes in shape as well as motion.

Revision tips

  • Review the definitions of push and pull and provide your own examples.
  • Categorize the forces mentioned in the exercises as contact or non-contact.
  • Draw simple diagrams to illustrate the effect of force in each scenario.
  • Focus on understanding the difference between forces that change motion and those that change shape.

Practice MCQs

Q1. Which of the following actions involves a 'pull' force?

Q2. When an archer stretches a bow, what change occurs in the bow?

Q3. Which type of force is applied when lifting a heavy object?

Q4. The force that pulls an arrow towards the Earth after it is released is due to:

Q5. Which of these is an example of a non-contact force?

Frequently asked questions

What is the main concept covered in CBSE Class 8 Science Chapter 11?

Chapter 11 focuses on the concept of force, explaining it as a push or pull that can change an object's state of motion or shape. It also introduces different types of forces like contact and non-contact forces.

What are the two main effects of force discussed in this chapter?

The two main effects of force are changing the state of motion of an object (making it move faster, slower, or change direction) and changing the shape of an object.

Can you give examples of contact forces from the chapter?

Yes, examples of contact forces include muscular force (used for pushing or pulling) and frictional force, which arises when surfaces are in contact.

What are non-contact forces?

Non-contact forces are forces that act on an object without physical contact. Examples include gravitational force (like the Earth pulling an apple), magnetic force (between magnets), and electrostatic force (between charged objects).

How do these NCERT Solutions help Class 8 students?

These solutions provide clear, step-by-step explanations for each exercise question, helping students understand the concepts of force and pressure better and prepare effectively for their exams.

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