A 55 kg woman cheats on her diet and eats a 584 Calorie (584 kcal) jelly donut f
ID: 1419347 • Letter: A
Question
A 55 kg woman cheats on her diet and eats a 584 Calorie (584 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 30% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast?
__________stairs
Explanation / Answer
mass m=55kg
(a) ans
one jelly doughnut contains 584 cal
therefore the one jelly doughnut =584*10^3*4.2 j=2452.8 joules
(b) ans
mass m=55 kg
energy=mgh
2452.8*=55**9.8 H
height H=4.55 m
therefore the no.of stairs=4.55/0.15=30.33 stairs
(c) ans
30/100=w/Q
30/100=w/2452.8
w=735.84 J
therefore the work =mgH
735.84=55*9.8*H
the height h=1.37 m
the no.of stairs =1.37/0.15=9.13 stairs
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