Question

A block of weight $5N$ is pushed against a vertical wall by a force $12N$. The coefficient of friction between the wall and block is 0.6. The magnitude of the force exerted by the wall on the block is

• A. $12N$
• B. $5N$
• C. $7.2N$
• D. $13N$

Answer 1

The correct option is D $13N$

$\text{N}=$ applied force $=12N$
$\therefore f_{\text{max}}=\mu \text{N}=0.6\times 12=7.2N$
Since, weight $w<f_{\text{max}}$
$\therefore$ Force of friction $f=5N$
$\therefore$ Net contact force $=\sqrt{{\text{N}}^2+f^2}$
$=\sqrt{(12{)}^2+(5{)}^2}=13N$