A 60kg skater begins a spin with an angular speed of 6.0 rad/s. By changing the position of her arms, the skater decreases her moment of inertia by 50%. What is the skater's final angular speed? I(initial)ω(initial) = I(final)ω(final) I used 60 kg as my inertia, is inertia and mass interchangeable in this example? Then I used 30kg because her inertia is 1/2 in the final inertia 60 (6.0) = 30ω 360 = 30ω ω = 12 rad/sec I said above but my biggest problem with this equation is it seems to simple, I did not think mass and inertia were able to be interchangeable, but there is no radius or time given so I am not sure what else I could solve for. If my answer is correct, why is inertia and mass equal in this example?