1. The problem statement, all variables and given/known data This is just a general case I'm having trouble trying to imagine: https://lh3.googleusercontent.com/-mTyOwzfLy0E/VluaNlxEddI/AAAAAAAAAEk/2Creguw3xzY/w530-h174-p-rw/Screenshot%2Bfrom%2B2015-11-29%2B21%253A34%253A50.png Suppose there is a cylinder, kind of like a yo-yo, that is being pulled by a massless string. The string does not slip and the yo-yo is rolling without slipping on top of a plank, there is no friction between the plank and the horizontal surface. 2. Relevant equations Torque, Pure rotating condition 3. The attempt at a solution My question is: since the plank does slips over the horizontal surface, then Is the velocity of the cylinder's centre of mass = 0 ? (Assuming Tension < Static Friction between the cylinder and the plank) It's worth mentioning that the problem doesn't say anything about friction between the plank and the yo-yo, but I thought there must be friction because of the rolling without slipping condition Thank you!