Question

Frictional force on a body can be zero when

• A. normal reaction is equal to zero
• B. the body is moving in vaccum
• C. the body is moving through a liquid
• D. all of these

Answer 1

Answer: (A), (B)

The correct options are
A

normal reaction is equal to zero

B

the body is moving in vaccum

Friction comes into play only when there is relative motion between two bodies. In vaccum, there is nothing to oppose the movement of body through it. So, frictional force on the body is zero. Also, when the normal reaction is zero, frictional force will be zero.