A ball bounces because it changes shape on impact and the momentum from changing the shape back to normal makes it go up again. Then why rock solid stuff also bounce when dropped? Ive seen pebbles bounce when dropped. My phone bounces like 1 or 2 times when i drop it. Why?
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You’ve got it kind of backwards. If everything were perfectly rigid and never deformed, then everything would bounce back to the spot it was dropped from. That is called an “elastic collision”. A bouncy ball is able to get close to a truly elastic collision by not permanently deforming, like you said.
But relatively rigid things can bounce even better than the bouncy ball, like a steel ball bearing, it bounces incredibly well on a steel plate, because there’s no where else for the energy to go.
What causes stuff to *not* bounce is that the energy goes somewhere else. Either it cracks the screen in your phone’s case, deforms the ground in the case of a padded floor, or a bunch of other things.
But the default state of something hitting the ground is for it to bounce back. The energy has to specifically go somewhere else in order for it not to bounce.
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