- #1
Domnu
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Problem
If you throw a ball with velocity v at a wall, it rebounds with the same speed, v. What happens if you throw it at speed v towards a wall which is traveling towards you at speed w? What is your answer in the limit in which w is much larger than v?
Answer
Let us work in the frame of the wall. The ball comes towards you at velocity v+w, so it must leave at velocity v+w with respect to you. Moving back to the lab frame, this means that the ball moves now, to the left with velocity v+2w. In the limit where w is much larger than v, the velocity of the ball is 2w.
Is my answer correct?
If you throw a ball with velocity v at a wall, it rebounds with the same speed, v. What happens if you throw it at speed v towards a wall which is traveling towards you at speed w? What is your answer in the limit in which w is much larger than v?
Answer
Let us work in the frame of the wall. The ball comes towards you at velocity v+w, so it must leave at velocity v+w with respect to you. Moving back to the lab frame, this means that the ball moves now, to the left with velocity v+2w. In the limit where w is much larger than v, the velocity of the ball is 2w.
Is my answer correct?