Work and Power Gym

Lift a weight quickly, then slowly. Did you do more work? Time your lifts and compare your power with a light bulb and a horse.

Work done
0 J
Time
0.00 s
Power
Lift it!
Horsepower
–

The maths, live

Work W = m × g × hW = 20 × 9.81 × 1.2 = 235 J
Power P = W ÷ tP = 235 ÷ 2.0 = 118 W
Horsepower = P ÷ 746118 ÷ 746 = 0.16 hp

Lift the same weight slowly, then quickly. The work is the same, but which lift has more power?

How it works

Lifting something does work against gravity. The work done equals the weight times the height: W = m × g × h, measured in joules (J). It doesn't matter how fast you lift it, the work is the same.

Power is how fast you do the work: P = W ÷ t, measured in watts (W). One watt is one joule every second. An old light bulb uses 60 W, a person running upstairs manages around 200 to 500 W for a few seconds, and one horsepower is about 746 W.

Try this

  1. Lift 20 kg to 1 m in 5 s, then in 1 s. Which lift does more work? Which needs more power?
  2. Can you lift with the same power as a horse?
  3. Drag the bar up yourself as fast as you can. How many old light bulbs could your power light?