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.
Force of Friction
The force of friction is the force exerted by a surface as an object moves across it or attempts to move across it. This force acts parallel to the surface and opposite to the direction of motion or attempted motion. The magnitude of friction depends primarily on two factors: the nature of the surfaces in contact and the normal force pressing the surfaces together. The rougher the surfaces, the greater the friction. Similarly, the greater the normal force, the higher the frictional force. Importantly, friction does not depend on the area of contact between the surfaces. When a force is applied to an object resting on a surface, friction increases to oppose it up to a maximum limit, known as limiting friction. Beyond this limit, the object starts moving and kinetic friction acts, which is usually less than limiting friction. Friction converts kinetic energy into heat, which is why rubbing hands together produces warmth.
📊 Diagram: Diagram showing a block on a surface with forces labeled: applied force, frictional force opposing it, and normal force perpendicular to the surface.
🧪 Activity: No specific activity here, but the concept is foundational for later experiments.
🔗 Connection: Leads to the next section 'Types of Friction' which explains different friction types in detail.
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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