Question

A block of mass 3 kg is placed on the floor of coefficient of static friction is 0.4. The force of 3.5 N applied on the block. Calculate the force of friction and discuss the motion of the body.

• A. 3.5 N, moves
• B. 3.5 N, remains at rest
• C. 11.76, moves
• D. 11.76 N, it remains at rest

Answer 1

The correct option is B 3.5 N, remains at rest

block is placed on the horizontal plane, so $mg=N$

also maximum friction force is $\mu .N=0.4\times 3\times 10=12N$.

but friction force acts only if there is a tendency of motion. so friction force will be equal to force applied until it reaches its maximum value. After that limiting friction will act and body will start moving.

So $3.5<12$, hence friction acting is 3.5N and body will not move.