Question

Two forces of 6 N and 3 N are acting on the two blocks of 2 kg and 1 kg kept on frictionless floor. What is the force exerted on 2 kg block by 1 kg block?

• A. 1 N
• B. 2 N
• C. 4 N
• D. 5 N

Answer 1

The correct option is C 4 N

The forces exerted by each block on the other block are shown in the figure.

Net external force acting on the system $F=F_2-F_1$

$\therefore$ $F=6-3=3N$

Total mass of the system $M=1+2=3kg$

Thus acceleration of the system $a=\frac{F}{M}=\frac{3}{3}=1m/s^2$

Equation of motion for block of mass $m_2=2kg$ :

$m_{2}a=F_2-N_1$

Or $2\left(1\right)=6-N_1$

$⟹$ $N_1=4$ N

Thus 1 kg block exerts a force of $4$ N on 2 kg block.