Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 1.95 gal of gasoline. Only 38.5% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. Suppose the energy content of gasoline is 1.20 10 J/gal. Part 1 + To solve the problems below it will be necessary to first determine the amount of useful work that is provided by the gasoline. How much useful work is provided by the gasoline? Part 2 What is the magnitude of the force exerted to keep the car moving at constant speed? Part 3 If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 22.0 m/s? (Enter the unit as gal)