Motion of Connected Bodies - NEET Physics Questions

Question 1:

Three blocks A, B and C of masses 4 kg, 2 kg and 1 kg respectively, are in contact on a frictionless surface, as shown. If a force of 14 N is
applied on the 4 kg block, then the contact force between A and B is

connected body nlm

1. 18 N

2. 2 N

3. 8 N

4. 6 N

View Answer

The total mass of the system:

$M = 4 + 2 + 1 = 7 \text{ kg}$

The acceleration of the system:

$a = \frac{\text{Total Force}}{\text{Total Mass}} = \frac{14}{7} = 2 \text{ m/s}^2$

Now, considering block B and C together (mass =

$2 + 1 = 3$

kg), the force required to accelerate them:

$F_{AB} = (3 \times 2) = 6 \text{ N}$

Thus, the contact force between A and B is 6 N.