From: utzoo!decvax!ucbvax!npois!harpo!utah-cs!utah-gr!thomas Newsgroups: net.misc Title: Re: Two ball problem. Article-I.D.: utah-gr.429 Posted: Wed May 26 12:42:07 1982 Received: Sat May 29 09:18:36 1982 Well, now, seems to me you could measure the moment of inertia of each ball. The one with the greater moment would be the hollow one. =Spencer