Question

Which requires more work, lifting a 90 kg bag up 6 m in 4 minutes, or lifting a 45 kg bag up 12 m in 2 minutes?

Answer 1

W = m g h increase in PE due to lfting bag

W1 = 90 kg * 9.8 m/s^2 * 6 m

W2 = 45 kg * 9.8 m/s^2 * 12 m

W2 / W1 = 1 the work is the same in both cases

The power required is different

P = W / t

Since t is smaller for W2 and the work output is the same the power required to produce W2 is twice as great