F.5Physics Work and Power 40
2010-11-06 10:16 pm
A lift of mass 1000 kg carries 8 passengers from the 5th floor to the 12th floor of a buliding in 8s. The average mass of the passengers is 70 kg and the height of each storey is 3.5 m. Estimate the minimum power needed by the lift.
回答 (1)
2010-11-06 11:35 pm
✔ 最佳答案
Height travelled by the lift when going from the 5th floor to 12th floor= 3.5 x 7 m = 24.5 m
Total mass of lift and passengers
= (1000 + 8 x 70) kg
= 1560 kg
Hence, gain in potential energy
= 1560g x 24.5 J = 382 200 J
where g is the acceleration due to gravity, taken to be 10 m/s2
Minimum power needed
= energy delivered /time
= 382200/8 watts = 47775 watts = 48 kw
收錄日期: 2021-04-29 17:36:46
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