[问答题]
A wheel of mass M has radius R. It is standing6qknwxv4 ;v mu z21g3iq;gmv/ ve6e7 8+.qkrg .:phkqogt 3zrrsrtically on the floor, and we want to exert a horizontal force F at its axle so that it will climb a step against which it rests (Fig. 8–55). Tk6.+ 8keg :7qzgrr toh3p.srqhe step has height h, where h