1. The problem statement, all variables and given/known data I'm trying to find the frequency of a hoop pivoting on an axle. The hoop has mass M and radius R. 2. Relevant equations 3. The attempt at a solution Obviously f = ω / 2pi But apparently ω=sqrt(MgL/I), which you plug into the above. I don't understand where this part comes from, though. L is the center of gravity of the hoop (which is just R). Any help?