[问答题]
A wheel of mass M ha5gx 57hqa4 jgys radius R. It is standi a hji w91);jsareu5l*ng vertically on the floor, and we want to exwhi19sejjra ; a5) *ulert a horizontal force F at its axle so that it will climb a step against which it rests (Fig. 8–55). The step has height h, where h