Here's the problem and I'm close to the answer, but I guess close isn't good enough on a Physics exam.(adsbygoogle = window.adsbygoogle || []).push({});

A spinning solid disk, rotating with angular velocity Wo, is put down on a level surface. It slides and rolls until it reaches an angular velocity W at which it rolls without sliding. Show that W = Wo/3

I place my origin on the ground so that angular momentum is conserved.

The disk spins clockwise

1 = right when the disk is placed on the floor.

2 = right when the disk begins rolling without spinning.

L = angular momentum.

cm = center of mass.

I = moment of inertia about cm

R = radius

M = Mass

V = Velocity of cm

L1spin + L1cm = L2spin + L2cm

IWo + 0 = IW - RMV ==> with no slip V = RW

(2/5)MWoR^2 = (2/5)MWR^2 - MWR^2

-2Wo/3 = W

Besides probably messing up the signs, why do I end up with twice what I need?

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# Spinning Disk

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