如图,工人用一个定滑轮和动滑轮组成滑轮组,把重为500N的箱子匀速提升5m,动滑轮的质量为8kg,不计绳重和摩擦,去g=
6个回答

(1) F=1/2(G物+G动)= 1/2(G物+m动g)=1/2(500N+8Kg×10N/kg)=290N

(2) η=G物/( G物+G动)=500N/(500N+80N)=86%