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PBRMEASAP
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I am trying to figure out which way a spinning dinner plate (idealized as a disk) precesses when you toss it in the air. I can figure out the rate of precession in terms of the spin rate and the angle the spin axis makes with the precession axis. I believe it is [tex]\Omega_{pr} \cos{\theta} = 2 \Omega_{sp}[/tex]. The question is, if you toss a clockwise-spinning plate at a shallow angle, does it precess clockwise or counterclockwise? I tried adding up the torques on each mass element of the disk, and the requirement that the net torque vanishes indicates that the precession is counterclockwise. However, when I tried it with a real plate, it looked like the precession was clockwise. Of course, it precesses pretty fast and the wobbles are small, so it's hard to see. I taped a plastic drinking straw to the center of the plate (sticking up) to make the precession easier to see, and got the same result. Any ideas?