Question

A $3kg$ block is placed over a $10kg$ block and both are placed on a smooth horizontal surface. The coefficient of friction between the blocks is $0.2$. If a horizontal force of $20N$ is applied to $3kg$ block, accelerations of the two bodies in ${ms}^{-2}$ are:
($g=10{ms}^{-2}$)

• A. $\frac{14}{3},3$
• B. $\frac{13}{4},3$
• C. $\frac{14}{3},0.6$
• D. $\frac{13}{4},0.6$

Answer 1

The correct option is C $\frac{14}{3},0.6$

Force of friction between the blocks $f$ =$\mu N=0.2\times 3\times 10$

$=6N$

This force acts in backward direction on lighter block and in forward direction on heavier block.

Thus $ma=F-f$

$⟹3a=20-6=14$

$⟹a=\frac{14}{3}m/s^2$
And for second body,
$ma=f$

$⟹10a=6$

$⟹a=0.6m/s^2$