CBSE Class 8 Science Exemplar Chapter 11: Force NCERT Solutions

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NCERT Solutions PDF Class 8 PDF

This chapter, 'Force,' for CBSE Class 8 Science Exemplar, delves into the fundamental concepts of forces and their effects. The NCERT Solutions provided here cover multiple-choice questions and explanations related to applied forces, magnetic forces, and electrostatic forces. Students will learn to identify the type of force responsible for various phenomena, such as the movement of objects and the interaction between charged bodies. These solutions offer clear explanations and step-by-step reasoning, aiding students in grasping the core principles of force and motion. They are designed to help students prepare effectively for their examinations by reinforcing their understanding of these crucial physics concepts.

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Quick info

BoardCBSE
ClassClass 8
SubjectScience Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 11

Chapter summary

Chapter 11 of the CBSE Class 8 Science Exemplar focuses on the concept of Force. The NCERT Solutions for this chapter explain different types of forces, including applied forces, magnetic forces, and electrostatic forces. The solutions clarify how these forces cause motion or changes in the state of objects, using examples like a block moving due to applied forces and a hammer striking a gong due to magnetic force. It also touches upon electrostatic forces experienced during activities like combing hair.

Learning outcomes

  • Understand the concept of applied force and its effect on motion.
  • Identify the role of magnetic force in causing movement.
  • Explain the phenomenon of electrostatic force and its applications.
  • Differentiate between various types of forces based on their effects.

Topics covered

Paper topics

  • Force
  • Applied Force
  • Magnetic Force
  • Electrostatic Force
  • Force and Motion
  • Types of Forces

Important topics

  • Applied Force
  • Magnetic Force
  • Electrostatic Force
  • Identifying Forces in Scenarios

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Questions and Solutions

Multiple Choice Questions

1. In Fig 11.1, two boys A and B are shown applying force on a block. If the block moves towards the right, which one of the following statements is correct?

(a) Magnitude of force applied by A is greater than that of B.

(b) Magnitude of force applied by A is smaller than that of B.

(c) Net force on the block is towards A.

(d) Magnitude of force applied by A is equal to that of B.

(Note: Figure 11.1 is assumed to show boy A applying force from the left and boy B from the right, with the block moving towards the right.)

Solution: The correct answer is (a). When a block moves in a particular direction, it means the net force acting on it is in that direction. In this scenario, the block moves towards the right. This indicates that the force applied by boy A (pushing from the left) is greater in magnitude than the force applied by boy B (pushing from the right). The difference between these two forces results in a net force towards the right, causing the block's movement.

2. In the circuit shown in Fig.11.2, when the circuit is completed, the hammer strikes the gong. Which of the following force is responsible for the movement of hammer?

(a) gravitational force alone

(b) electrostatic force alone

(c) magnetic force alone

(d) frictional force alone

(Note: Figure 11.2 shows an electric circuit with a coil and a hammer mechanism.)

Solution: The correct answer is (c) magnetic force alone. When the electric circuit is completed, an electric current flows through the coil. This current makes the coil behave like an electromagnet. The electromagnet then produces a magnetic field, which exerts a magnetic force on the hammer, causing it to move and strike the gong.

3. During dry weather, while combing hair, sometimes we experience hair flying apart. The force responsible for this is

(a) force of gravity.

(b) electrostatic force.

(c) force of friction.

(d) magnetic force.

Solution: The correct answer is (b) electrostatic force. When you comb your hair, especially in dry weather, the friction between the comb and your hair can cause a transfer of electric charges. This results in both the comb and your hair becoming electrically charged, often with opposite charges. These charges then interact, leading to repulsion between the hair strands, causing them to fly apart due to the electrostatic force.

Common mistakes

  • Confusing different types of forces (e.g., magnetic vs. electrostatic).
  • Incorrectly determining the direction or magnitude of net force.
  • Attributing motion to a single force when multiple forces are involved.

Revision tips

  • Review the definitions and examples of applied, magnetic, and electrostatic forces.
  • Pay close attention to the diagrams provided in the questions to understand force interactions.
  • Practice identifying the dominant force responsible for observed effects.
  • Use the explanations to reinforce your understanding of why a particular force is at play.

Practice MCQs

Q1. In Fig 11.1, if a block moves towards the right when two boys A and B apply force, which statement is correct regarding the forces applied?

Q2. In the circuit shown in Fig. 11.2, a hammer strikes a gong when the circuit is completed. Which force is primarily responsible for this movement?

Q3. During dry weather, hair sometimes flies apart when combed. What type of force causes this phenomenon?

Frequently asked questions

What is the main topic of CBSE Class 8 Science Exemplar Chapter 11?

Chapter 11 of the CBSE Class 8 Science Exemplar focuses on the concept of Force, explaining its different types and effects on objects.

Which types of forces are discussed in these NCERT Solutions?

These solutions discuss applied force, magnetic force, and electrostatic force, explaining their roles in various physical phenomena.

How do these solutions help students prepare for exams?

The solutions provide clear explanations for multiple-choice questions, helping students understand the underlying principles of forces and how to apply them to solve problems, which is crucial for exam preparation.

What is the significance of Fig 11.1 in the context of forces?

Fig 11.1 illustrates how the net force determines the direction of motion when multiple forces are applied. If the block moves right, the force applied from the right side (by boy A) is greater than the force applied from the left (by boy B).

Why is magnetic force responsible for the hammer striking the gong in Fig 11.2?

In Fig 11.2, the electric current flowing through the coil creates an electromagnet, which then exerts a magnetic force on the hammer, causing it to move and strike the gong.

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