5.1 A car is traveling along a highway at 65 miles per hour. Theroad is horizontal (0% slope). If the wind resistance and rollingresistance at the wheels creates a combined resistive force of 950N, what is the power (kW) developed at the rear wheels?
5.2 How much power (kW) must the car engine in problem 5.1develop if the overall mechanical efficiency of the transmissionand drive train is 94%?
5.3 Assume the car engine in problem 5.1 is operated on gasolinewith an energy content of 113,500 Btu's per gallon, and that thethermal efficiency of the spark ignition engine and drivetrain is28.6%. What is the fuel efficiency of the car in miles pergallon?
5.4 The car in problem 5.1 approaches a mountain and beginsascending a grade of 6.0%. If the car maintains an uphill speed of70 miles per hour, how much additional power (kW) must be developedby the engine to overcome the change in elevation? Assume the carhas a mass of 1400 kg.
5.5 Assume the car above is operated on a blend of 85% ethanoland 15% gasoline (E85). If the energy content of ethanol is 80,460Btu's per gallon, what is the energy content of the E85 fuel(Btu/gal)?
5.6 Assume the overall thermal efficiency of the engine anddrivetrain of the car above drops to 24.5% when operated on E85fuel. What is the estimated fuel economy (km/L) of the car abovewhen subjected to the uphill operating conditions above (Problem5.4)?
