What are they? I have some poeple telling me that for a cylinder it's I = (1/4)MR2 + (1/12)ML2 and that for a disk it's the same. Other people have told me that it's I = (1/2)MR2 for a disk and that it's the same for a cylinder. In the past I've used the former and have gotten the right answers on my homework but I used the same equation for a question i'm stuck on and got the incorrect answer. I just want some clarification on this, I'd really appreciate it.