[问答题]
A wheel of mass M has radius R. It i g),3gtin ff oqs qy4v gv:qs/x-..j6us standing .r8nnxha4 dm* vertically 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). r4nnd mh*a8x.The step has height h, where h