A 58-kg woman cheats on her diet and eats a 705-Calorie (705 kcal) jelly doughnu

Question

A 58-kg woman cheats on her diet and eats a 705-Calorie (705 kcal) jelly doughnut 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 26% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast? stairs

Explanation / Answer

mass of the woman, m=58 kg

a)

enegry E=705 calorie

E=705 Kcal

E=705*10^3 cal

E=705000*(4.184 J)

E=2.95*10^6 J

b)

height of the single stair, h=15cm

enegry, E=m*g*H

2.95*10^6=m*g*H

2.95*10^6=m*g*H

2.95*10^6=58*9.8*H

===>

H=5190 m

===>

no of stair, n=5190/0.15

n=34600

c)

efficiency e=26%

===>

mechanical enegry, E=(0.26*2.95*10^6)

E=7.67*10^5 J

and

m*g*h=7.67*10^5

58*9.8*h=7.67*10^5

====> h=1349.4 m

no of stairs, n=1349.4/(0.15)

n=8996 ----->

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.