Question

A block placed on a rough horizontal table is acted upon by an external horizontal force $P$. The graph of frictional force $F$ against external force $P$ is

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

$i)$ When a small amount of force $P$ is applied, the block will not move but the friction force will act and it is called static friction.
$ii)$ It will increase linearly with force $P$ until it reaches the limiting friction $F_l$.
$iii)$ When the force is applied beyond the limiting friction, the block will start to move but friction force will slightly decrease and thereafter it will remain constant and it is called kinetic friction. $F_k$

So (D) is the correct graph.