Warp wrote:
>   What I don't understand is how a rotating object can produce heat but
> still maintain its full angular momentum. You have not explained this
> at all.

Angular momentum consists of both velocity and distance. When the skater 
pulls her arms in and speeds up, the muscular energy turns into kinetic 
energy, but the angular momentum stays the same. When the spinning disk 
rubs against the disk spinning the other way, the kinetic energy of the 
disks is turned into the kinetic energy of the individual atoms (i.e., 
heat), but the positive-signed spinning of the top disk cancels the 
negative-signed spinning of the bottom disk.

So, you can change energy without changing angular momentum by spinning 
faster but closer, or by having two things spinning opposite directions 
change their rate of spin the same amount in different directions.

Energy, on the other hand, isn't signed (except in some rather bizarre 
circumstances, and to make the math come out for potential energy in 
situations that never actually occur in reality), so that's how it can 
happen that you can change the form of energy without changing the 
amount of angular momentum.

-- 
   Darren New / San Diego, CA, USA (PST)
     Remember the good old days, when we
     used to complain about cryptography
     being export-restricted?

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