Question

P and Q are two identical masses at rest suspended by an inextensible string passing over a smooth frictionless pulley. Mass P is given a downward push with a speed v as shown in figure. It collides elastically with the floor and rebounds immediately. What happens immediately after collision?

• A. P and Q both move upwards with equal speed.
• B. P and Q both move upwards with different speeds.
• C. P moves upwards and Q moves downwards with equal speeds.
• D. Both P and Q are at test.

Answer 1

The correct option is A P and Q both move upwards with equal speed.

Since collision is elastic, P will move upward with velocity v after the collision and Q will be moving with speed v in upward position at that time. Hence P and Q both move upwards with same speed.