A gallon of gasoline has a chemical PE of 1.2 x 10^8 J. If a 2000 kg car gets 40 km/gallon, what is the average force on the car? Assume constant speed and remember the force on the car is applied over the total distance traveled. What is the coefficient of friction? I tried PE = mgx, using m = 2000 and solving for x (which was 6122.45). I'm not really sure where to go from there though.