In which of the following situations is friction not useful?

A. Operation of a grinding machine
B. Walking
C. Application of brakes
D. Moving piston in a sleeve

Correct Answer:

Option D – Moving piston in a sleeve

Explanation

friction, force that resists the sliding or rolling of one solid object over another.

Examples of friction in our daily life

• Driving a vehicle on a surface.
• Applying brakes to stop a moving vehicle.
• Skating.
• Walking on the road.