Physics, Efficiency. ?

2020-06-01 8:27 pm

A machine marked with the effect 5500W lifts a stone that weighs 450kg to 4.2m which takes 5.3 seconds. What is the machines efficiency?

回答 (1)

2020-06-01 8:40 pm

Take g = 9.81 m/s²

Output power
= m g h / t
= 450 × 9.81 × 4.2 / 5.3 W
= 3500 W

Efficiency = (3500/5500) × 100% = 64% (to 2 sig. fig.)

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