[问答题]
A wheel of mass M hasn z5pe6ym:l+pr-b5j d ya*i 8c radt+u 6 -wr0t9*gjun 7fffr n(ou fzgk20ius R. It is standing vertically on the floor, and we want to exert a horizontal force F at its ak*f2j07+ ot gu ffu6urgnf0wt(-zr n9 xle so that it will climb a step against which it rests (Fig. 8–55). The step has height h, where h