Question

question 8
energy is stored in food as the potential energy of the electrical bonds in molecules. your body converts food energy to mechanical energy and heat. food energy is expressed in \calories,\ which are actually kilocalories (kcal, with 1 kcal = 4.186 kj). (a) how many joules are in a 130 - kcal serving of breakfast cereal? (b) a glass of 1% milk contains 130 kcal. how many glasses would a 62 - kg person have to drink to get the energy needed to climb a hill 125 m high, assuming all the milks energy is converted to her potential energy? show your work for credit.

Explanation:

Step1: Calculate the potential energy needed to climb the hill

The potential - energy formula is $U = mgh$, where $m = 62\ kg$, $g=9.8\ m/s^{2}$, and $h = 125\ m$.
$U=62\ kg\times9.8\ m/s^{2}\times125\ m$
$U = 62\times9.8\times125\ J=75950\ J$.
Convert this energy to kilocalories. Since $1\ kcal = 4186\ J$, then $U=\frac{75950\ J}{4186\ J/kcal}\approx18.14\ kcal$.

Step2: Determine the number of glasses of milk

Each glass of milk contains $130\ kcal$. Let $n$ be the number of glasses of milk.
We use the formula $n=\frac{\text{Total energy needed}}{\text{Energy per glass}}$.
$n=\frac{18.14\ kcal}{130\ kcal}\approx0.14$ glasses.

Answer:

Approximately 0.14 glasses.