Angular PE?

[justadream]

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TBR Physics I page 210 #44

A person is on a rotating platform and extends his arms to increase by 3 times.

Since L = Iw, his angular velocity (w) decreases to 1/3 the original value.

Angular KE also decreases since
New KE = .5(3I) * (1/3)^2 = one-third of original KE

So where does this lost KE go? Does it go into angular PE?

 

[Cawolf]

The energy is used to perform work and move his arms outward.

If he moves his arms inwards to decrease the moment of inertia and increase angular velocity - he is doing work to increase the energy.