Question

A force $\overrightarrow{F}=\hat{i}+4\hat{j}$ acts on block shown. Determine the force of friction acting on the block is :

• A. $-\hat{i}$
• B. $-1.8\hat{i}$
• C. $-2.4\hat{i}$
• D. $-3\hat{i}$

Answer 1

The correct option is A $-\hat{i}$

Normal force,

$N=(mg-4)\hat{j}$$=(10-4)\hat{j}$$=6\hat{j}$

Limiting friction,

$f=\mu N=0.3\times 6(-\hat{j})=1.8(-\hat{i})$

Here horizontal force = $1N$ less than the limiting frictional value hence frictional force acting F = horizontal force of friction

$f=1(-\hat{i})N$