a car travels 108km at 30.0m/s. 2.20galons of gas are used. only 30% of the gas goes into useful work to keep the car moving. The energy content of gasoline is 1.30 * 10^8 J per gallon. What is the force in N exerted to keep the car moving at a constant speed? If the required force is directly proportional to speed how many gallons would be used to drive 108km at 28m/s