Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site oddjob.UChicago.UUCP Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!gargoyle!oddjob!matt From: matt@oddjob.UChicago.UUCP (Matt Crawford) Newsgroups: net.physics Subject: Re: Conservation of momentum Message-ID: <375@oddjob.UChicago.UUCP> Date: Tue, 14-Aug-84 22:09:43 EDT Article-I.D.: oddjob.375 Posted: Tue Aug 14 22:09:43 1984 Date-Received: Wed, 15-Aug-84 07:03:16 EDT References: <268@heurikon.UUCP> Organization: U. Chicago: Astronomy & Astrophysics Lines: 27 Actually, you are talking about the law of conservation of ANGULAR momentum, angular momentum being conserved separately from linear momentum. Here is an experiment you can try to demonstrate to your- self what is happening to cats and divers when they are falling: Take a wheel from a bicycle and attach some sort of axle by which you can hold it. Now sit in a reasonably well-lubricated swivel chair, holding the wheel's axis vertical. Now grab a spoke and give the wheel a spin. You will begin to turn in the other direction. If you can't manage the bike whhel, do this instead: sit back in the swivel chair with your legs up and with a heavy book in your hands. (I am using Misner, Thorne and Wheeler's GRAVITA- TION.) Slowly hold the book out to one side, then smoothly swing it in front of you and around to the other side. Bring it back in to your lap and extend it out to the original side again. Repeat until enlightenment is acheived. All the while, your total angular momentum is zero (ignoring friction), yet the angle your are facing changes. If you want to get some net angular momentum you can hold the book out and fling it to one side, with a velocity perpendicular to the direction from you to it. (This will hurt your shoulder, I think.) ___________________________________________________________ Matt University ARPA: crawford@anl-mcs.arpa Crawford of Chicago UUCP: ihnp4!oddjob!matt