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According to Car and Driver, the 2023 Shelby GT500 engine develops 760hp at an engine rotational speed of 7300rpm. The wheels are P305/35YR20. The weight of the car is 4183lbf. The frontal area is 29ft². The drag coefficient is Cd=0.32. Assume a rolling resistance =0.015. The gear ratios of the transmission and final drive are:

a.) Find the maximum theoretical speed in each of the 8 gears if the engine is turning at 7300rpm.

b.) Find the power needed at the theoretical maximum speed in each gear. Convert to units of horsepower.

c.) The literature implies that the car gets 21 miles per gallon at 65mph. Assume that gasoline has an energy density of 129,000BTU/gallon. What is the power needed to move the car at 65mph, overcoming drag and rolling resistance? How much energy (power times time) is needed to drive 18 miles at this rate of power use? Give answer in hp. Hint: how much time does it take to drive 18 miles at 65mph?

d.) Find the % efficiency of the engine - divide the energy (power times time) needed to travel 18 miles at 65mph in this car by the 129,000 BTU/gal of gas it needed to burn to do so. Is this car very efficient? Hint: get the energies into the same units.

e.) The 2023 Shelby GT500 costs $80,795 for the base model. If you can afford this, do you care about gas mileage?

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