44-kg woman cheats on her diet and eats a 695-calorie (695 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 28% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast? stairss..com/question/index? qid=20091118160038aazycd1

(a) how many joules of energy are the equivalent of one jelly doughnut?

We are already given the energy which is equal to 695 kcal. We know that in 1 kcal, there is 4184 Joules, therefore:

Energy = 695 kcal * (4184 J / 1 kcal)

Energy = 2,907,880 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

We can solve this by using the Potential Energy formula:

PE = m g h

2,907,880 J = 44 kg * 9.8 m/s^2 * h

h = 6,743.7 m

So the number of stairs is:

stairs = 6,743.7 m / 0.15 m

stairs = 44,958

(c) if the human body is only 28% efficient in converting chemical energy to mechanical energy, how many stairs must the woman climb to work off her breakfast?

So the number of stairs will be:

stairs = 44,958 / 0.28

stairs = 160,564