Chapter 9, Problem 42P

Ballet A ballet student with her arms and a leg extended spins with an initial rotational speed of 1.0 rev/s. As the draws her arms and leg in toward her body, her rotational inertia becomes $0.80\text{kg}\cdot {\text{m}}^2$ and her rotational velocity is 4.0 rev/s. Determine her initial rotational inertia.