Concept explainers
Fuel used to counter air resistance The resistive drag force that the air exerts on an automobile is
One liter of gas releases about
J of energy. So the gasoline energy that is equivalent to the resistive thermal energy produced during this trip is
In summary, you use about one-quarter gallon of gasoline to counter air resistance during the 160-km trip. Unfortunately, the car is only about 13% efficient, where
Consequently, your useful output of 0.98 liters requires an energy input of (0.98 L)/0.13=7.5 L of gas to overcome this air resistance. This is about half of the gasoline a typical car consumes when driving at a steady speed for 160 km. The other half is needed to overcome rolling resistance.
The amount of fuel used to counter air resistance should do what?
a. Increase in proportion to the speed squared
b. Increase in proportion to the speed
c. Be the same independent of the speed
d. Decrease in proportion to the inverse of the speed
e. Decrease in proportion to the inverse of the speed squared
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