A 58 kg woman cheats on her diet and eats a 459 Calorie (459 kcal) jelly donut f

Question

A 58 kg woman cheats on her diet and eats a 459 Calorie (459 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 25% 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 in joules = E = 459 x 10^3 x 4.184 = 1920456 Joules b. E = mgh height = h = 3378.71 stairs

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