Before you are two balls, one solid and one hollow. They are to all appearences completely identical: same size, same weight, same outer material (though one might assume, correctly, that the hollow ball would need a higher-density material on the inside to make it the same weight).

Without breaking either of the balls, how can you easily determine which is hollow?

Assume that the material is solid enough that a hitting the side of the hollow ball will not result in any noticeable echo or vibrations.

(In reply to Summary by Larry)

Larry, you are right,I did not realise this when I submitted my answer, but I'm not sure if this (my answer, that is) violates the given conditions (hitting the ball et al).

Maybe one could try with gamma rays?

Posted by Rex on 2005-03-27 14:57:50