1. The problem statement, all variables and given/known data If you start a coin rolling on a table with care, you can make it roll in a circle. The coin "leans" inward, with its axis tilted. The radius of the coin is b. The radius of the circle traced by the coin's center of mass is R, and the velocity of its center of mass is v. The coin rolls without slipping. Find the angle [itex]\phi[/itex] that the coin's axis makes with the horizontal. 2. Relevant equations 3. The attempt at a solution Here is my attempt at a solution: (attached) A correct solution that I understand and agree with is given here: https://www.physicsforums.com/showthread.php?t=365994. The only difference between that solution and my own is that instead of choosing the point of contact to be the center of my coordinate system, I chose the center of mass of the coin. I cannot figure out why my answer is 1/3 of his/hers and I would be very happy if you could point out the flaw in my reasoning.