posted by anonymous .
A crane lifts a concrete hopper of mass 370 kg from the ground to the top of a 38 m building that is under construction. The hopper moves with a constant speed during the lift. The power rating of the crane motor is 8.2 kiloWatts.
How long does it take for the crane to lift the hopper to the top of the building?
(Work per hopper load)/(Time) = 8200 W
Time = M g H/P
about 17 seconds