1. The problem statement, all variables and given/known data A cylinder with moment of inertia I, mass M, and radius r is being pulled by a string with a tension T. What is the acceleration of the cylinder? What is the force of friction? 2. Relevant equations Fnet = M*a = T - f Torque = I*(a/r) = f*r 3. The attempt at a solution So a = f*r^2/I And M*(f*r^2/I) = T- f. What I don't understand is how "f" (friction) slows the cylinder. It is just causing rotation, not acting on the center of mass. I thought my professor said that rolling friction doesn't slow things down... Thanks.