Question

A force $F=(\hat{i}+4\hat{j})\text{N}$ acts on the block shown. The force of friction acting on the block is :

• A. $-\hat{i}\text{N}$
• B. $-18\hat{i}\text{N}$
• C. $-2.4\hat{i}\text{N}$
• D. $-3\hat{i}\text{N}$

Answer 1

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


As given in fig.
Normal force,
$N=(10-4)\hat{j}=6\hat{j}$
Maximum friction force,
$f=\mu N(-\hat{i})=0.3\times 6(-\hat{i})=1.8(-\hat{i}))$
Maximum firctional force is $f>1\text{N}$ , so the frictional force act only equal to the force in $(+\hat{i})$ direction but in opposite direction;
$f=1(-\hat{i}\text{N})$.