Question

The blocks $A$ & $B$ have masses of $2$ & $6kg$ respectively are kept on a rough horizontal surface of $\mu =\mathrm{0.2.}$ If a horizontal force of $6N$ pushes them, calculate:
a) the acceleration of the system
b) the force that the $2kg$ block exerts on the other block. [Consider both cases, see figure].

Answer 1

The coefficient of friction of surface, $\mu =0.2$

Total mass of the system M= (2+6)kg = 8kg

Friction force f= $\mu Nsin90$

f= $0.2\times 8\times 10\times 1=16N$

Applied horizontal force on the block is F= 6N

Here applied force is not able to overcome the frictional force. So There is no motion. Hence zero acceleration.

(b) The force applied by 2kg block on the other is, $F-\mu N$

$F_b=6-(0.2\times 2\times 10)=2N$