Let’s consider the same automobile as the last week. Assume the 2 gallons per ho

Question

Let’s consider the same automobile as the last week. Assume the 2 gallons per hour fuel consumption corresponds to a cruising speed 60 mph of the automobile. Assuming the air drag coefficient of the car is 0.27, with the following formula for the air drag force Drag force (Drag coefficient)(cross sectional area of the car)0.5 Velocity2 , air (a) Determine the drag force experienced by the car if it is a 2012 Audi A6 2012 Avant (http://www.caricos.com/cars/a/audi/2012_audi_a6_avant/1920x1080/72.html) (b) Determine the power output from the engine to sustain this drag force under the specified speed. (c) Determine the first law efficiency of the engine based on your calculation in report#1 and the answer in part (b) of this report. If this value is less than 15% (which is lower than the realistic values), explain why.

Explanation / Answer

Let the density of air = 1.2 kg/m3

v = 5/18 * 96.5 = 26.8 m/s

A= 2.74 m2 (approx)

Drag force = 0.5 *0.27*2.74 *26.82 = 265.8 N

Power = Drag force* Velocity = 265.8* 26.8 =7123.44 W

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