   Chapter 5, Problem 73AP

Chapter
Section
Textbook Problem

In terms of 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 he were 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 × 108 J/gal. Find the fuel economy in equivalent miles per gallon for a person (a) walking and (b) bicycling.

(a)

To determine
The fuel economy in equivalent miles per gallon for a person who is walking.

Explanation

Given Info:

220kcal/h is required for walking 3.0mi/h

1kcal is equal to 4186J

Gasoline yields 1.30×108J/gal

When the person walks 3.0mile , the quantity of gasoline which could furnish the energy used for walking is,

V1=Ew1.30×108J/gal       (I)

• Ew is the energy used by the person for walking a 3.0mile distance

Formula to calculate the fuel economy of the walker is,

Fe=3.0miV1       (II)

On substituting equation (I) in (II),

Fe=3

(b)

To determine
The fuel economy in equivalent miles per gallon for a person who is bicycling.

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