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Re: The Olympics



Mark Sylvester wrote:

The difference between the translational and rotational cases is that you
can change the moments of inertia of the upper and lower parts of the body
by extending and retracting arms and legs. So extend arms, retract legs....
twist upper body right, lower body left.... retract arms, extend
legs.... twist upper body left, lower body right. You end up with a net
rotation. I've seen strobe photographs somewhere of a cat doing this.

I need to wrestle with this one a bit. What you say makes sense (the
ability to change 'I' is a big difference), but on the other hand it
seems paradoxical. If we have somebody with zero initial angular
momentum and they can as an isolated body execute a 180 degree turn
(then another, then another) then they are obtaining a net average
angular velocity while maintaining zero angular momentum. Hmmm... this
doesn't seem to be what the divers are doing but its interesting.


\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\

Doug Craigen
http://www.dctech.com/physics/about_dc.html