A 65-kg woman cheats on her diet and eats a 612-Calorie (612 kcal) jelly doughnu

Question

A 65-kg woman cheats on her diet and eats a 612-Calorie (612 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 21% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast?
stairs

Explanation / Answer

(a)1 kcal = 4184 joules

612kcal = 612* 4184 = 2560608 joules

(b)

mgh = 2560608 ==> h = 2560608/(65 * 9.8) = 4019.8m

no of stairs = h/15* 10^-2 = 4019.8 *10^2/15 = 26799 stairs

(c)

21% stairs of 26799 then total stairs will be

26799*21/100 =5627.79 stairs

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

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