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. None of these
• D. zero

Answer 1

The correct option is D zero

Frictional force will be applicable only when two connected surface try to do their realtive motion with respect to each other. Here there is no external horizontal force on the block. So there is no attempt of the relative motion. Both the block and the connecting surface are at rest. So frictional force on the block is zero.