Lifting power
A student lifts a 2.0 kg object vertically through a height of 3.0 m at constant speed. The lift takes 4.0 s. Take g = 9.81 m s⁻².
Calculate:
a) the work done on the object;
b) the average power developed.
Worked answer
Solution
- Step 1
W = mgh. - Step 2
W = 2.0 × 9.81 × 3.0 = 58.9 J. - Step 3
P = W / t = 58.9 / 4.0 = 14.7 W.
Final answer
Work done = 58.9 J; average power = 14.7 W.
Common mistake
Confusing the force mg with the work done.
Concepts tested
- work
- gravitational potential energy
- power
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