Consider a hollow cylinder of mass M with an outer radius R_out = 10 cm and an unknown inner radius R_in. If the hollow cylinder is to roll down an incline in the same time as a spherical shell of the same mass and the same outer radius, calculate R_in.
I_cyl = MR^2/2 .
I_shell = 3/5(MR^2)
The Attempt at a Solution
I think the inertia of each are equal but i'm not sure