1. The problem statement, all variables and given/known data Derive and show that the period for a thick ring would be T=2π√[d/g+(ΔR)^2/4Rg] 2. Relevant equations I'm not sure.... 3. The attempt at a solution Obviously, delta R means the difference between Ri and Ro would be considerable. So ΔR=Ro-Ri. Then Ro=R+ΔR/2 and Ri=R-ΔR/2 I also know that T=2π√(I/mgr) and Itotal=Icenter of mass + MR^2........ Can you guys help me? I'm lost here. Thanks a lot.