In terms of saving energy, bicycling and walking are far more efficient means of
ID: 1655650 • Letter: I
Question
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 186J). 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 1.30x10 J/gal. Find the fuel economy in equivalent miles per gallon for a person (a) walking and (b) bicycling. PLEASE SHOW FORMULAS PRIOR TO EACH PROBLEM THANKS!
Explanation / Answer
1 galllon yields 1.30e8 J = (1.30e8/ 4186) kcal = 3.11e+4 kcals
1 kcal requires 3.22e-5 gallons
a)
Walking at 3 mi/h requires about 220 kcal/h
3 miles /220 kcal = 0.0136 miles /kca
l 0.0136 miles /kcal = 0.0136 miles /(3.22e-5 gallons) = 422.4 miles /gallon
b)
Riding at 10 mi/h, a cyclist uses food energy at a rate of about 400 kcal/h
10 miles / 400 kcal = 0.025 miles / kcal
0.025 miles / kcal = 0.025 miles / (3.22e-5 gallons) = 776.4 miles / gallon
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