[问答题]
A wheel of mass M han6,ypk v.u2e cs r hw)*0fe 3wzb,c 6y17bcbdnjj adius R. It is standing vertically on the floor, and we want to exert a horizontal force F at its axle so that it will climb a step7fwebw y,*jdj)b3hc nc016 zb against which it rests (Fig. 8–55). The step has height h, where h