A lead ball and a rubber ball having same mass, collide normally with a vertical wall with the same velocityh. The lead ball falls down after striking, but the rubber ball bounces back.
Then which of the following is true and why?
1. The momentum of lead ball is greater than that of rubber ball
2. The momentum of rubber ball is greater than that of lead ball.
3. The rubber ball sufferes a greater change in momentum as compared to the lead ball
4. Both the balls suffer an equal change in momentum
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UP 0 DOWN 0 1 3
3 Answers
62hmm.. this is simple..
just discuss which ones will not be true...
some are very simple to be eliminated..
3 and 4 are very very simply eleiminated.... why?
1See, consider the metal ball:
let both of them be thrown with a velocity v (say)
Then, change in momentum of the metal ball = mv-0 = mv (its assumed to fall perpendicularly downwards, though it actually does not, but in reality, it falls literally downwards, with negligible velocity in the horizontal direction)
Consider rubber ball:
Initial momentum = mv.
Finally, it rebounds in the same direction, so it'll have some component of velocity in the reverse direction, say -v' (- sign indicates reverse direction)
So change in momentum = mv + mv' which is obviously greater than that of metal ball :)
anser is b)
:)
