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.

No, Joshua. The key here is momentum.

In my high school physics class, we learned how angular momentum is better conserved in a ring than a solid disc. There are many kinematic equations involving momentum for all sorts of rods, discs, spheres both holow and solid.

All one has to do is let them both go from an initial velocity of 0 from the same point on a fairly long incline plane. The solid sphere will accelerate faster.

Posted by Aerik on 2006-03-14 02:18:47