My experience with swinging two balls on the Cradle is that two balls swing out, answer B below. What's different about swinging one double-weight ball instead? The mass & angular momentum should be the same as two plain balls. The details of the collision will be different (propagation & reflection of the compression wave), but I thought the answer was determined by M & L. Rich -----Original Message----- From: math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] On Behalf Of Gary Antonick Sent: Thursday, December 09, 2010 10:44 AM To: math-fun Subject: [math-fun] why did everyone (except Bill) get this wrong? Hi all, I recently posed a simple mechanics question to a bunch of university faculty. Pretty much everyone got it wrong. What I'm wondering is.. why? Am trying to explore this a bit. Might make an interesting story. Here's the question. You have a Newton's Cradle. The first ball has twice the mass it normally would. You swing it so it hits the second ball. What happens? a. the last ball flies out b. the last two balls fly out c. something else Turns out the answer is c. No one gets this right. OK. Bill Gosper got it right. In fact, he's completely unraveling the problem. And Neil Bickford was essentially there. Maybe I should have asked more people in math-fun. But I asked 20 university faculty (physics and engineering, mainly) and they all got it wrong. Except one guy who had to simulate it first. What's going on? - Gary _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun