A 60-kg woman eats a 490 Calorie (490 kcal) jelly doughnut for breakfast (Need H

Question

A 60-kg woman eats a 490 Calorie (490 kcal) jelly doughnut for breakfast (Need Help w/ part B and C).

(a) How many joules of energy are the equivalent of one jelly doughnut?     
2032520        J    

(b) How many steps must the woman climb on a very tall stairway to change the gravitational potential energy of the woman-Earth system by a value 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 24% efficient in converting chemical potential energy to mechanical energy, how many steps must the woman climb to work off her breakfast?

_________ stairs

Explanation / Answer

a) Converting kcal into joules

E = (490 ) ( 4180 ) = 2048200 J

b) The number of steps is

n = E/ m g h = 2048200 / (60)(9.8)(0.15)

n = 23222 stairs

c) If the human body is 24% efficient then

n= 23222/0.24 = 96759 stairs

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