[问答题]
A wheel of mass M has radis0mc s)g8jkr 1g se;(ius ,fkwmht (0fx139 pccxR. It is standing vertically on the floor, and we want to exert a horizontal force F at its axle soxt wc0 ck9h1 fm(3pxf, that it will climb a step against which it rests (Fig. 8–55). The step has height h, where h