A 55-kg student eats a 540-Calorie (540 kcal) jelly doughnut for breakfast. (a)  How many joules of energy are the equivalent of one jelly doughnut? (b) How many stairs must the student 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. (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?

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Asked Dec 25, 2019
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A 55-kg student eats a 540-Calorie (540 kcal) jelly doughnut for breakfast. (a)  How many joules of energy are the equivalent of one jelly doughnut? (b) How many stairs must the student 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. (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?

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Expert Answer

Step 1

a)

The required energy is,

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3(540x10° cal) 4.186 J 1 cal = 2.26x10° J

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Step 2

b)

The required num...

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n= mgh 2.26x10 (55)(9.8)(0.15) s 27953

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Work,Power and Energy

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