For saving energy, bicycling and walking are far more efficient means of transpo
ID: 1897546 • Letter: F
Question
For saving energy, bicycling and walking are far more efficient means of transportation than is travel by
For saving energy, bicycling and walking are far more efficient means of transportation than is travel by automobile. For example, when riding at 12.5 mi/h, a cyclist uses food energy at a rate of about 360 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 = 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 1.30 108 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/gal Please show all worrkExplanation / 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