A construction crane lifts 120 identical concrete blocks
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A construction crane lifts 120 identical concrete blocks, each of mass 25\,kg, from the ground to the roof of a building 20\,m high. The entire lifting operation takes exactly 2.0\,min. The electric motor driving the crane draws a steady power of 8.0\,kW during this time. Take g=9.8ms−2.
(i) Calculate the total work done in raising the 120 blocks to the roof.
(ii) Determine the average power actually delivered in performing this lifting work.
(iii) Using your answers to (i) and (ii), find the efficiency of the lifting operation of the crane.