A warehouse crane is used to raise a 250 kg crate vertically through a height of 8.0 m
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A warehouse crane is used to raise a 250 kg crate vertically through a height of 8.0 m. In one trial the crate is lifted in 16 s; in a second trial an identical crate is lifted through the same height in 4.0 s.
Assume that the upward force exerted by the crane’s cable just balances the weight of the crate and that air resistance is negligible.
(a) Describe how the amount of work done by the crane in each trial compares. Explain your reasoning without performing a numerical calculation.
(b) Using your description from part (a), explain why the average power developed by the crane differs between the two trials, even though the work done is the same.
(c) Suppose the height were doubled while the lifting times remained 16 s and 4.0 s, respectively. Describe qualitatively how the average power in each trial would change compared with the original situation and justify your answer.