A hoist lifts a 500 kg load through 12 m at constant speed in 20 s. Taking the gravitational acceleration as 9.8 m/s per second, what average power does the hoist deliver?

1. The load moves at constant speed, so the lifting force just balances the weight of the load. 2. The weight is the mass multiplied by the gravitational acceleration. 3. That is 500 kilograms multiplied by 9.8 metres per second per second, which is 4900 newtons. 4. The work done is the force multiplied by the height, so it is 4900 newtons multiplied by 12 metres. 5. That gives 58 800 joules of work transferred to the load. 6. Power is the rate at which work is done, so it is 58 800 joules divided by 20 seconds. 7. That equals 2940 watts. 8. The 5880 watt answer traps anyone who divides by 10 seconds, the 1470 watt answer traps anyone who divides by 40 seconds, and the 300 watt answer forgets the gravitational acceleration entirely. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 5: Work, energy and power_