when cruising at 75 mi/h on a highway, a car\'s engine develops 45 hp. If this e
ID: 1589552 • Letter: W
Question
when cruising at 75 mi/h on a highway, a car's engine develops 45 hp. If this engine has a thermodynamic efficiency of 25% and 1 gal of gasoline has an energy content of 1.3 x 10^8 J, what is the fuel efficiency in mpg of this car? when cruising at 75 mi/h on a highway, a car's engine develops 45 hp. If this engine has a thermodynamic efficiency of 25% and 1 gal of gasoline has an energy content of 1.3 x 10^8 J, what is the fuel efficiency in mpg of this car? when cruising at 75 mi/h on a highway, a car's engine develops 45 hp. If this engine has a thermodynamic efficiency of 25% and 1 gal of gasoline has an energy content of 1.3 x 10^8 J, what is the fuel efficiency in mpg of this car?Explanation / Answer
Energy available per gallon for car, E = efficiency * energy content per gallon of gasoline
=> E = 0.25 * 1.3*108 = 3.25*107 J
45 hp = 45 * 746 W = 33570 W. Or work done per second = 33570 J
Hence work done per hour = 3600s * 33570 J = 120852000 J.
Since car consumes 120852000 J energy to travel 75 miles,
hence distance traveled by consuming 3.25*107 J energy, d = 75 mi* 3.25*107 J / 120852000 J = 20 miles
Hence fuel efficiency of of car = 20 mpg
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