Question

If $100N$ force is applied on the block then frictional force acting on the block will be (in Newton):

Answer 1

Answer: 100

The normal force of the weight is given by,
$N=30g=30\times 10=300N$ ; where $g$ is acceleration due to gravity.
The static frictional force on the block will be,
$f_s={\mu }_{s}N=0.4\times 300=120N$
The kinetic frictional force will be,
$f_k={\mu }_{k}N=0.3\times 300=90N$
The applied force is $F=100N$ .
Since, $f_s>F$ , therefore, the block will not move and frictional force on block will be $100N$ .