1 . 1min内起重机将重物提升的高度是多少? H = vt = 1.5 * 60 =90m2 . 1min内起重机做了多少有用功? W = mgH = 500 * 10 * 90 = 450000 J 3 . 若起重机的效率为60%,它的总功率多大? Wo = W/0.6 =75000J P = Wo/t = 1250 W