[问答题]
A wheel of mass M has raddg;(tdarug68 x nd r++iel xnyvr1ng.p,l.)e,k 3j +taus 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 ley+.k, )3tve1gjrxnp,l. nastep against which it rests (Fig. 8–55). The step has height h, where h