1. The problem statement, all variables and given/known data I am stuck on this problem involving tension, acceleration of a system, friction and a pulley. I have an idea of how to find the acceleration of the system neglecting the mass of the pulley, but it is not the solution. How does adding a frictionless pulley in the system change its acceleration? 2. Relevant equations F=ma torque = I(alpha) rotational equations? 3. The attempt at a solution For the tension T1 from the pulley disk downwards to mass m, the tension is mg. For the tension T2 from the mass M rightward to the pulley disk, would the tension be equal to T1? I drew FBD's for the two masses. For M, by applying Newton's 2nd Law, Fnet=Ma: T2-f = Ma For m, applying F=ma: mg-T1 = ma I know the acceleration of the system should be equal. But how do I incorporate the pulley disk in the system to find the acceleration of the system?