[问答题]
A wheel of mass M has radius R. It is standing vertically on the floor, and ws g),q lv-v4mf jy:ti um(b7b5e mpvt q0;p-hi/9 om(z fwant to exert a horizontal force F at its axle so that it will climb a step against which it rests (Fig. 8–55). hv0z qop(/ipf9t m-;m The step has height h, where h
