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.

Put them both in a bucket of water.  The hollow ball will float and the solid ball will sink.

I'll leave it as an excersize to the readers to decide why this answer is wrong. ;)

Posted by Erik O. on 2005-03-25 17:30:09