(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
