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# physics help?

A student ( m=85 kg) runs up the stairs (h= 2.8 m) in 1.42 seconds.

a) Calculate the Energy change of the student.

b) Calculate the efficiency of the student if it took 9339 J of chemical potential energy for the student to run up the stairs

c) Calculate the output power of the student in horsepower ( 1 h.p=746 W)

d) in the lab you walked up a flight of stairs to determine your own power. describe two reasons why the efficiency of the climb was not 100%

### 1 Answer

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- NCSLv 71 month agoFavorite Answer
a) ΔE = mgΔh = 85kg*9.8m/s²*2.8m = 2332 J

b) ε = 100% * 2332/9339 = 25%

c) P = 2332J / 1.42s = 1642 W

d) The efficiency can never be 100%. You burn energy even without climbing stairs.

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