A 2005 Chrysler Town and Country MInivan has a frontal area of 2.9m2 and a drag
ID: 1829239 • Letter: A
Question
A 2005 Chrysler Town and Country MInivan has a frontal area of 2.9m2 and a drag coefficient of 0.35. A 2000 Honda Insight has a frontal area of 1.9m2 and a drag coefficient of 0.25. Determine the amount of money saved per year associated with aerodynamic drag reduction as a result of switching from the Chrysler to the Honda. Assume 12,000 miles per year at an average speed of 55 miles per hour. Use this gasoline data: price $3.50/gal, energy content 1.3 x10^8 J/gal. Assume an engine efficiency of 30%. Note the savings you would estimate by simply looking up the "miles per gallon" ratings of these cars may be higher due to the factors other than aerodynamic drag.
Explanation / Answer
Chrysler:
Energy Spend due to drag = 0.5 * Cd * d * v^2[ d = density of air ]
= 0.5 * 0.35 * 1.16 * (24.58 ^2) [ 55 miles/hour = 24.58 meters/sec ]
= 122.64 joules
at 30%efficiency energy given by 1 gal of gasoline = 0.3 * 1.3 *10^8
= 3.9 * 10^7
For 122.64J gasoline required = 122.64 / (3.9 * 10^ 7 )
= 31.44 * 10^(-7)
Honda:
Energy Spend due to drag = 0.5 * Cd * d * v^2[ d = density of air ]
= 0.5 * 0.25 * 1.16 * (24.58 ^2) [ 55 miles/hour = 24.58 meters/sec ]
= 87.6 joules
at 30%efficiency energy given by 1 gal of gasoline = 0.3 * 1.3 *10^8
= 3.9 * 10^7
For 122.64J gasoline required = 87.6 / (3.9 * 10^ 7 )
= 22.46 * 10^(-7)
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