A 58 kg woman cheats on her diet and eats a 527 Calorie (527 kcal) jelly donut f

Question

A 58 kg woman cheats on her diet and eats a 527 Calorie (527 kcal) jelly donut 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 27% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast?
stairs

Explanation / Answer

a) Energy=527*4186=2.2*106J

b)No. of stairs=Total energy/Gain in potential energy per stair climb=2.2*106/(58*9.8*0.15)=25874 stairs

c)No. of stairs=efficiency*Total energy/Gain in potential energy per stair climb=0.27*2.2*106/(58*9.8*0.15)=6986stairs

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