# Ping Pong ball through a bowling ball

1. Apr 21, 2010

### DrSammyD

What information would I need in order to calculate the speed necessary to go through a bowling ball, and how would I calculate it. Also, is there a speed that is fast enough that that ping pong ball doesn't get demolished? (such as the front of the ball having enough energy in itself to go through the bowling ball such that the back of the ball doesn't expend any energy going through it because there is already a hole in it?)

This isn't a homework question, it's just something I'm wondering about soft body physics.

2. Apr 22, 2010

### sophiecentaur

But the front of the pingpong ball will be slowed up a bit on impact because of Momentum conservation, however fast it's going. That will involve an internal force within the ball, which will cause deformation, surely. If it damages the bowling ball, then how could you suggest that the pingpong ball could ever be unscathed? What if the bowling ball were fired at the pingpong ball? In the observational frame of the centre of mass of the two together, it would be the same situation.
There would, of course, be a speed at which the pingpong ball would 'penetrate' through the bowling ball - but it would come out of the other side in a sorry state.

3. Apr 25, 2010

### DrSammyD

Well I'm thinking of when a karate expert punches through a bunch of bricks, and doesn't hurt his hand, but if he goes two slow, he can break his hand because he hasn't punched through the bricks and all of that energy is immediately put back into his hand instead of over the course of time of the breaking.

4. Apr 26, 2010

### sophiecentaur

There must be a lot more to the Karate situation. I think my simple argument shows what happens in the ping pong ball situation.
In Karate there is a lot of strength and psychology involved but there are clear limits to what can actually be achieved. You still need to apply the Physics rigorously to the situation.