Rotational Equilibrium and Dynamics -

[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 ?
ω=angular speed.. so ω=12.0 rad/s
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

 

[Gamma]

s the formula KE=1/2·I·ω² ?

yes

so then how would i get I (inertia) ?

its given. read the question

and how would i find out initial and final ?

Use conservation of Angular momentum.

 

[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?