Question

Three blocks of masses 3 kg, 2 kg and 1 kg are placed side by side in contact with each other on a smooth horizontal surface with the 3 kg block on the left extreme and 1 kg block on the right extreme. A horizontal force of 12 N is applied on the 3 kg block pushing it towards the 2 kg block, the contact force between the 2 kg block and 1 kg block is

• A. 6 N
• B. 4 N
• C. 2 N
• D. 8 N

Answer 1

Answer: (C)

2 N

For block A, $F=M_{T}a$ where a, acceleration of the system and $M_T$ is total mass of the system.
$a=\frac{12}{3+2+1}=2m/s^2$

Consider block B, the contact force between 2kg and 1 kg is $T_c=1a=2N$