[问答题]
A wheel of mass M has(kxo 24ht.rzw:yog- z radiuvh rmhl qkg16jg 4.o;bh+9 (zqs R. It is standing vertically on the floor, and we want to exert a horizontal force F at its axle so that it will climb a step against whicqhr 6(v4hgb gq.lz9m1k+o h; jh it rests (Fig. 8–55). The step has height h, where h