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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)

### 1 Answer

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- billrussell42Lv 71 month ago
work = mgh = 85•9.8•2.8 J

efficiency in perceht = 100(85•9.8•2.8/9339) =____%

power = work/time = 85•9.8•2.8/1.42 = ___ watts

or 85•9.8•2.8/1.42 watts x 1 HP/746 w = ___ HP

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