A lift is used to carry boxes to the top floor of a hotel 20m high.A total weight of 100kg of boxes was carried up in 20 seconds.If the useful output of the engine driving the lift mechanism is 1.2 kilowatt,calculate the eficiency of the engine of the lift mechanism
power = m * g * h / time = 100 kg * 9.8 m/s^2 * 20 m / 20 s = 980 W
efficiency = (980 / 1200) * 100%