## Related questions with answers

For saving energy, bicycling and walking are far more efficient means of transportation than is travel by automobile. For example, when riding at 10.0 mi/h, a cyclist uses food energy at a rate of about 400 kcal/h above what he would use if merely sitting still. (In exercise physiology, power is often measured in kcal/h rather than in watts. Here 1 kcal = 1 nutritionist’s Calorie = 4 186 J.) Walking at 3.00 mi/h requires about 220 kcal/h. It is interesting to compare these values with the energy consumption required for travel by car. Gasoline yields about $1.30 \times 108$ J/gal. Find the fuel economy in equivalent miles per gallon for a person (a) walking and (b) bicycling.

Solution

Verifieda)

Lets convert the power of the person walking from kcal/h to J/h:

$\begin{align*} P_w&=220\frac{\,\text{kcal}}{\,\text{h}}\cdot \frac{4186\,\text{J}}{1\,\text{kcal}}\\ &=920920\frac{\,\text{J}}{\,\text{h}} \end{align*}$

Next, lets convert the J/h into gal/h:

$\begin{align*} P_w&=920920\frac{\,\text{J}}{\,\text{h}} \cdot \frac{1\,\text{gal}}{1.3\cdot 10^{8}\,\text{J}}\\ &=7.084\cdot 10^{-3}\frac{\,\text{gal}}{\,\text{h}} \end{align*}$

Person walks 3 miles in one hour, so he does :

$\begin{align*} N_w&=\frac{3\frac{\,\text{mi}}{\,\text{h}}}{7.084\cdot 10^{-3}\frac{\,\text{gal}}{\,\text{h}}}\\ &=\boxed{423.49\frac{\,\text{mi}}{\,\text{gal}}} \end{align*}$

## Create a free account to view solutions

## Create a free account to view solutions

## Recommended textbook solutions

#### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

4th Edition•ISBN: 9780133942651 (8 more)Randall D. Knight#### Mathematical Methods in the Physical Sciences

3rd Edition•ISBN: 9780471198260 (1 more)Mary L. Boas#### Principles of Physics

4th Edition•ISBN: 9780534491437 (8 more)John W. Jewett, Raymond A. Serway#### Fundamentals of Physics

10th Edition•ISBN: 9781118230718 (3 more)David Halliday, Jearl Walker, Robert Resnick## More related questions

- differential equations

1/4

- differential equations

1/7