Okay, I'm no physics whiz, and this has me stumped. You know those toy airplanes you can get with the rubber-band driven propellers? You twist the propeller a bunch of times, and this stores potential energy in the rubber band. Then when you let go of the rubber band, it drives the propeller.
Well, suppose you have two of these airplanes. They are identical except for the fact that airplane A has an extremely efficient bearing which holds the rotating propeller shaft. The other airplane (B) has a "normal" bearing, which is less efficient. Thus, the shaft on B generates more heat when it spins the shaft.
You take both systems and wind the propeller 100 times, then let go. Shaft A spins with almost no friction. It therefore uses up it's energy faster, and it spins through it's 100 counter-rotations in maybe 5 seconds. Shaft B takes 10 seconds to do the same thing. BOTH shafts started with 100 "shaft-spin units" stored in their rubber bands at the start. 10 seconds later, each has done 100 shaft spins. Shaft B is hotter, though, due to the friction.
My question: Since both systems started with the same potential energy, where did the "extra" energy go in shaft A? Remember, they both did 100 spins. Shaft A did it faster, but it still did the same amount of spins. Maybe it's leftover in shaft A's angular momentum at the end? (remember, I'm not a physics guy - be nice if it turns out "angular momentum" isn't the proper term!) :-)
Maybe shaft B only does 99.9 counter-spins, losing 0.01 spin-units to friction? Am I making some incorrect assumption?