Question

A block of mass 4 kg is kept on a rough horizontal surface. A horizontal force of 19.6 N is just able to slide the block.
In a force of 16 N acts then what is the frictional force acting on the block?

• A. 16 N
• B. 3.6 N
• C. 19.6 N
• D. can't predict as the value of coefficient of kinetic friction is not given

Answer 1

The correct option is A 16 N

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

also maximum friction force is $\mu .N$, which is given 19.6.

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 $16<19.6$, hence answer is 16N.