功 W = F S = P t 1J = 1N•m = 1W•s功率 P = W / t = Fυ 1KW = 103 W,1MW = 103KW有用功 W有用 = G h（竖直提升）= F S（水平移动）= W总 – W额 =ηW总额外功 W额 = W总 – W有 = G动 h（忽略轮轴间摩...