Consider the system on the attached file. I did an assignment with it, which made me think a lot. So the spring like thing in the cylinder is a torsional spring, which when released produces a certain torque round the cylinder making it rotate. But that creates a friction and assuming a high enough coefficient of friction it will start to roll. One then had to assume that: Ffriction * R = I * α (1) To find the angular acceleration. Writing up the equations for the linear acceleration this was possible to find. However! Is (1) really correct? Because what about the friction in the small wheels of the wagon. Don't their friction also contribute to the linear acceleration of the system yet not the angular?