A 56 kg woman cheats on her diet and eats a 562 Calorie (562 kcal) jelly donut f

Question

A 56 kg woman cheats on her diet and eats a 562 Calorie (562 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)

m=56 kg

E=562KCal

=562*10^3 cal

but,

1 Calorie=4.1868 J

now,

E=562**10^3*4.1868 J

=2352.98*10^3 J

=2.35*10^6 J

b)

h=15 cm

E=m*g*h .....is the energy for single step

let N is no.of steps

====>

N(m*g*h)=2.35*10^6

N=(2.35*10^6)/(m*g*h)

=(2.35*10^6)/(56*9.8*0.15)

=28583.33 stairs

c)

hear efficiency is 25%

now,

E=(2352.98*10^3)*22%

E=(2352.98*10^3)*0.22

=517655.6 Joule of energy convert in to mechanical energy

now,

N(m*g*h)=E

N=E/(m*g*h)

=517655.6/(56*9.8*0.15)

=6288.33 stairs

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