申論題

1. A uniform solid cylinder with mass of M and radius of 2R rests on a flat tabletop. A string wrapped around the cylinder runs over a uniform disk-shaped pulley with mass M and radius R that is mounted on a frictionless axle through its center. A block of mass M is suspended from the free end of the string (Fig. 1). The string doesn't slip over the pulley surface, and the cylinder rolls without slipping on the tabletop (Assume the string is massless and inextensible). The system is released from rest at t0 = 0.0 s. At time t, find:

(b) the magnitude and the direction of the static friction force acted on the cylinder ,