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ScienceClass 8FRICTION

FRICTION | Class 8 Science Notes

By ConceptScroll Team · Published on 17 July 2026 · 2 min read

FRICTION – this guide gives you a concise, exam-ready overview of FRICTION from Class 8 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.

What is Friction?

Friction is defined as the force that opposes the relative motion or tendency of motion between two surfaces in contact. It acts tangentially to the surfaces and always in the direction opposite to the applied force or attempted motion. Friction arises because no surface is perfectly smooth; the microscopic roughness causes interlocking of surface irregularities. When a force is applied to move an object, friction resists this motion. The amount of friction depends on the nature of the surfaces and the force pressing them together, called the normal force. Friction can be beneficial, such as providing grip for walking, or detrimental, such as causing wear and energy loss in machines. There are two main types of friction: static friction, which acts when an object is at rest, and kinetic (sliding) friction, which acts when an object is moving.

📊 Diagram: Illustration showing a block resting on a surface with arrows indicating applied force and frictional force opposing it.

🧪 Activity: No specific activity in this section.

🔗 Connection: Prepares for the next section 'Force of Friction' which discusses the characteristics and behavior of frictional force.

Frequently asked questions

1. Fill in the blanks. (a) Friction opposes the __________ between the surfaces in contact with each other. (b) Friction depends on the __________ of surfaces. (c) Friction produces __________. (d) Sprinkling of powder on the carrom board ______ friction. (e) Sliding friction is __________ than the static friction.

(a) motion (b) nature (c) heat (d) reduces (e) less

2. Four children were asked to arrange forces due to rolling, static and sliding frictions in a decreasing order. Their arrangements are given below. Choose the correct arrangement. (a) rolling, static, sliding (b) rolling, sliding, static (c) static, sliding, rolling (d) sliding, static, rolling

static, sliding, rolling

3. Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be (a) wet marble floor, dry marble floor, newspaper and towel. (b) newspaper, towel, dry marble floor, wet marble floor. (c) towel, newspaper, dry marble floor, wet marble floor. (d) wet marble floor, dry marble floor, towel, newspaper

wet marble floor, dry marble floor, newspaper and towel.

4. Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

The frictional force acts upward along the surface of the desk, opposite to the direction of the sliding motion of the book (which is downward).

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