Lindsey H.

asked • 05/30/23

Physics Joules Energy

A 46-kg woman cheats on her diet and eats a 580-Calorie (580 kcal) jelly doughnut for breakfast.

(a) How many joules of energy are the equivalent of one jelly doughnut? 

 _________J 


(b) How many stairs must the woman climb to perform an amount of mechanical work equivalent to the food energy in one jelly doughnut? Assume the height of a single stair is 15 cm. 

 ________stairs 


(c) If the human body is only 26% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast? 

 ________stairs


Sanjay A.

for b) note work done per stair = 46 kg * 9.8 m/sec^2 * 0.15 m = WDPS Distance = <total-doughnut-energy>/WDPS Distance = 580kcal * 4184 J/cal / WDPS Distance = 580000 * 4184/ (46*9.8*0.15) #number of stars = Distance /0.15 comes out roughly 251 stairs let me know if any question Sanjay
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05/30/23

Sanjay A.

c) since body is only 26% efficient 26/100 = 251/x roughly 965 stairs. oh boy!
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05/30/23

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