A 1.60 102-kg piano is being lifted at a steady speed from ground level straight up to an apartment 18.0 m above the groundThe crane that is doing the lifting produces a steady power of 4.00 102 WHow much time does it take to lift the piano?
By definition power is a rate of energy flow PE/t then tE/P Energy equal to the work done against gravity or equal to potential energy Pe gained hence E Pe Pe mgh and finally tmgh/P t 1.60 E+2 x 9.81 x 18.0 / 4.00 E+2 t70.6 sec
