# Homework Help: Rotational Equilibrium and Dynamics -

1. Jan 19, 2006

### raconteur

Rotational Equilibrium and Dynamics - :)

I'm totally stumped!
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A skater spins with an angular speed of 12.0 rad/s with his arms outstretched. He lowers his arms, decreasing his moment of inertia from 41 kg·m² to 36 kg·m²

Calculate his initial and final rotational kinetic energy.
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Is the formula KE=1/2·I·ω² ?
so then how would i get I (inertia) ?
and how would i find out initial and final ?
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i just need some help :grumpy:

Last edited: Jan 19, 2006
2. Jan 20, 2006

### Gamma

yes

Use conservation of Angular momentum.

3. Jan 20, 2006

### raconteur

^^^
hmm, i think i get it

so.. i use (plug in) 41 kg·m² to get my initial and 36 kg·m² to my my final?