Test: Friction - 2 - Class 8 MCQ

• Friction is the force that resists the relative motion or tendency of such motion of two surfaces in contact.
• Friction occurs when two surfaces are in contact with each other.
• Friction can cause wear and tear on surfaces, generate heat, and affect the efficiency of machines.

• The frictional force exerted by fluids is also called as drag.
• This kinds of frictional force can be reduced by changing the shape of the moving body.

The treaded tyres of cars, trucks and bulldozers increase friction force between road and tyres and provide a better grip with the ground.
Friction is the resistance to motion of one object moving relative to another.
Friction is a resultant force not a fundamental one like the electromagnetic force.

• The shape of fish is streamlined that help in decreasing fluid friction.
• The narrower part of streamlined shape offer less resistance due to friction.

Carpenters while fixing screws, grease the tips of screen to decrease the friction. Grease present on screw reduce the friction offered by wood articles.

- Ball bearings are designed to reduce friction between moving parts in machines.
- They replace sliding friction with rolling friction, which is much lower.
- Sliding friction occurs when two surfaces move against each other.
- Rolling friction, present in ball bearings, involves spheres rolling over a surface.
- This reduction in friction minimizes wear and tear and increases efficiency.
- Thus, the correct answer is A: Sliding friction.

The substances which reduce friction are called lubricants. Lubricants include graphite, oils and greases. Lubricant stick with moving part to reduce friction.