Class 8 Science Chapter 9 Friction

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I. Chapter Summary:

The chapter “Friction” introduces students to the force of friction, which acts in the opposite direction of motion and resists the movement of objects. It explains how friction is both a helpful and opposing force. Students learn about different types of friction—static, sliding, rolling, and fluid friction, and how friction varies with the nature of surfaces and presence of lubricants. The chapter also discusses methods to increase or reduce friction depending on the requirement in various real-life situations.

II. Key Concepts Covered:

III. Important Questions:

(A) Multiple Choice Questions (1 Mark):

1. Friction always acts:
   a) In the direction of motion
   b) Perpendicular to the surface
   c) Opposite to the direction of motion ✔️
   d) In upward direction

2. Which friction is the highest?
   a) Sliding
   b) Static ✔️
   c) Rolling
   d) Fluid

3. Fluid friction can be reduced by:
   a) Increasing pressure
   b) Streamlining ✔️
   c) Lubricating
   d) Making surface rough

4. Which of the following is used to reduce friction?
   a) Sand
   b) Oil ✔️
   c) Cloth
   d) Rubber

(B) Short Answer Questions (2/3 Marks):

1. Define friction. Name two factors affecting it. (PYQ 2020)

2. Why is it difficult to walk on a smooth or wet floor?

3. Give two advantages and two disadvantages of friction. (PYQ 2019)

4. Why are wheels used in vehicles?

(C) Long Answer Questions (5 Marks):

1. Explain different types of friction with examples. (PYQ 2021)

2. How can we increase and reduce friction? Give examples.

3. What is fluid friction? How is it minimized in aircrafts and boats?

4. Why is static friction usually greater than rolling and sliding friction?

(D) HOTS (Higher Order Thinking Skills):

1. If friction is so useful, why do we try to reduce it in machines?

2. Why do gymnasts use powder on their hands before performing?

IV. Key Formulas/Concepts:

V. Deleted Portions (CBSE 2025–2026):

No portions have been deleted from this chapter as per the rationalized NCERT textbooks.

VI. Chapter-Wise Marks Bifurcation (Estimated – CBSE 2025–2026):

VII. Previous Year Questions (PYQs):

VIII. Real-World Application Examples to Connect with Topics:

• Car tyres are grooved to increase friction for better grip.

• Airplanes and fish have streamlined bodies to reduce fluid friction.

• Oil and grease in engines reduce wear and increase machine life.

• Sand on icy roads increases friction and prevents slipping.

IX. Student Tips & Strategies for Success (Class-Specific):

Time Management:

• Allocate time weekly to learn conceptual differences and examples of each friction type.

• Practice diagram labeling (e.g., streamlined shapes, friction arrows).

Exam Preparation:

• Revise advantages/disadvantages of friction using T-charts.

• Prepare real-life application questions for HOTS section.

Stress Management:

• Visualize friction around you (e.g., shoes on floor, brakes) to learn by observation.

• Do simple home experiments like rolling vs sliding objects.

X. Career Guidance & Exploration (Class-Specific):

For Class 9–10 Students:

Explore:

• CBSE Science Fairs, Model Exhibitions on Force & Motion, NTSE, STEM Clubs

XI. Important Notes:

• Learn diagrams of friction types (especially rolling vs sliding).

• Understand the cause-effect link between surface roughness and friction.

• Stay updated with ncert.nic.in and cbseacademic.nic.in.