A freely rotating merry-go-round on a playground has a moment of inertia of 312 kgm2 and a radius of R=2.5 m. It is rotating with ω0=2.8 rad/s when a kid of mass 45 kg is standing on its outer rim. Neglecting friction, what is going to be the angular velocity of the merry-go-round after she walked d=0.7 m toward the center?

Answer 1

I before: 312
I after: 312-45(2.5-.7)^2

conservation of momentum applies

momentumbefore=momentum after
312wo=(312-45(2.5-.7)^2)wf
solve for wf

Answer 2

So would I divide the problem by wf?