Posted by Ania on .
A crane whose motoer has a power input of 5.0kW lifts a 1200kg load of bricks through a height 30m in 90s. Find the efficency of the crane which is the ratio between its output power and its input power

physcis 
bobpursley,
power in lifting= mgh/time=1200*9.8*30/90
power input= 5kW
efficiency fraction= lifting power/5kw