[问答题]
A wheel of mass M hasqxk wh:4gcqyb-g4 /q :pyci,* uq6 t3 hzd ,t)uowj9s+radius R. It is standing vertically on the floor, and we want to exert a horizontal force F at its ax,u*, zqhs+6d wipo tctuy3j9 )le so that it will climb a step against which it rests (Fig. 8–55). The step has height h, where h