[问答题]
A wheel of mass M has radius R. s/4t,r5 ju; izp 7xxkxIt is standing vertically on th 4 bto.05fvxb oyoft2xy5+,le3wy3ihe 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). The step has height h, wherex55+ h.yey o033vwx4t2libt, bo yoff h
