I have two problems which appear equivalent, but apparently they are not. The first one is this: M, a solid cylinder (M=1.75 kg, R=0.131 m) pivots on a thin, fixed, frictionless bearing. A string wrapped around the cylinder pulls downward with a force F which equals the weight of a 0.750 kg mass, i.e., F = 7.357 N. Calculate the angular acceleration of the cylinder. The second one is this: If instead of the force F an actual mass m = 0.750 kg is hung from the string, find the angular acceleration of the cylinder. I know how to solve for the second one, but I don't know how to solve for the first because I see no difference between the two problems. Could anyone explain?