Question

Two stones A and B of masses 5 kg and 8 kg respectively are released from a height of 20 m above a thin plank.Assuming both masses sticks to the plank after collision in a time of 0.2s and a force of 600 N is required to break the plank. Choose the correct option.

• A. Stone A will break the plank ; Stone B will not
• B. Stone B will break the plank ; Stone A will not
• C. Both will be able to break the plank
• D. None of them will be able to break the plank

Answer 1

The correct option is B Stone B will break the plank ; Stone A will not

Final velocity= $\sqrt{2gh}$

Acceleration = -20/0.2 = 100 $m/s^2$

Force by A = mass x acceleration = 500 N

Similarly
Force by B = 800 N
Stone B will break the plank but Stone A will not be able to break it.