For saving energy, bicycling and walking are far more efficient means of transpo
ID: 1373531 • Letter: F
Question
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 410 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 nutritionists Calorie = 4186 J.) Walking at 3.20 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 x 10^8 J/gal. (a) Find the fuel economy in equivalent miles per gallon for a person ,walking. mi/gal (b) Find the fuel economy in equivalent miles per gallon for a person bicycling. mi/galExplanation / Answer
speed of riding , v = 10.5 mi/hr
a)
time taken to travel 1 mile , t = 1/3 hour
t = 0.333 hour
energy needed to go 1 mile = energy rate * time
energy needed to go 1 mile , E1 = 0.333 * 230kCal
energy needed to go 1 mile = 76.6 Kcal = 76.6* 4186 J
energy needed to go 1 mile = 320605 J
fuel economy = 1.3 *10^8/320605 mi/gallon
fuel economy = 405.5 mile/gallon
the fuel economy of the person walking is 405.5 mile/gallon
b)
time taken to travel 1 mile , t = 1/10.5 hour
t = 0.095 hour
energy needed to go 1 mile = energy rate * time
energy needed to go 1 mile , E1 = 380 * 0.095 kCal
energy needed to go 1 mile = 36.19 Kcal = 36.19 * 4186 J
energy needed to go 1 mile = 151493 J
fuel economy = 1.3 *10^8/151493 mi/gallon
fuel economy = 858.12 mile/gallon
the fuel economy of the person bicycling is 858.12 mile/gallon