A friend and I somehow got on this odd topic and we disagree on the answer. Here's the scenario we were thinking of. If we had 2 wheels that had the same physical dimensions of diameter and width, and the only difference was a considerable difference in mass, would one wheel spin longer on an axis than the other if you gave both of them the same amount of initial force to make them rotate? The bearings would also be the same. A specific example would be a wheel made of a light wood, like balsa, and another wheel made of steel. I told her I thought the wheel with more mass would spin longer, but she thinks they would spin at the amount of time. I guessed longer because isn't this basically the principle of how a flywheel works? I thought most flywheels were heavy just for this very reason. And as a separate but related question, does the weight distribution on the disk also make a difference on the length of spinning? So if most of the mass was towards the center, or the edges, or evenly distributed throughout, does this affect the spin times? I vaguely remember discussing this in physics class in high school, but that was over 30 years ago. The important matter is that whoever wins gets a bottle of wine. :) Thanks in advance for your replies.