Question

A block is at rest on a rough horizontal surface. There is no horizontal force on it. The weight of the block is 5 N. The frictional force on the block is _____.

• A. proportional to the normal force on the block
• B. proportional to the roughness of the surface and the block
• C. zero
• D. proportional to the area of contact of the block

Answer 1

The correct option is C zero

Frictional force will be applicable only when two surfaces in direct physical contact with each other undergoes relative motion. Here there is no external horizontal force on the block. So there is no relative motion. Both the block and the surface are at rest. So frictional force on the block is zero.