Question

You are raising up a big bucket of water from a 25.9 m deep well. The combined mass of the water and the bucket is 13.9 kg. The bucket is attached to a heavy duty steel chain. The mass of the chain is 19.3 kg.

1. How much work do you perform during the lifting process?
2. If it takes 1.75 minutes for you to raise the bucket of water out of the well, then what was your average power?

Answer 1

Wb = 13.9 kg * 25.9 m * 9.8 m/s^2 = 3530 Joules

(work required to remove bucket)

Center of mass of chain = 25.9 / 2 = 12.95 m height of CM of chain

Wc = 12.95 * 19.3 * 9.8 = 2450 Joules

(work required to remove chain)

Total work = 3530 + 2450 = 5980 Joules

P = W / t = 5980 J / 105 sec = 57 J/s = 57 Watts