In a factory, an electric motor is used to raise the boxes shown in Fig. 2.1. Diagram labels: motor, power supply, cable, boxes, cage. The boxes sit inside a cage, and the motor coils a cable round a cylinder to lift the cage and boxes. The combined mass of the boxes is 37 kg and they are lifted straight up through 13 m to a storage area.
(a(i))[1]
Calculate the total weight of the boxes.
(a(ii))[2]
Calculate the useful work done in lifting the boxes to the storage area.
(b(i))[2]
The e.m.f. of the power supply for the motor is 230 V. The current in the motor is 5.6 A. The motor takes 11 s to lift the cage and boxes to the storage area. Calculate the total electrical energy transferred to the motor in 11 s.
(b(ii))[1]
Calculate the percentage efficiency achieved by the lifting process.
(c)[2]
Some of the energy transferred by the motor during the lifting process is not transferred usefully. State two reasons why the lifting process has an efficiency below 100%.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “360 N is the correct total weight.” …