Please help -- Efficiency of car engine question... Unit test tomorrow 1. The problem statement, all variables and given/known data A car's engine is only 12% efficient at converting chemical energy in gasoline into mechanical energy. If it takes 18000 N of force to keep the car moving at a constant speed of 21 m/s, how much chemical energy would be needed to move the car a distance of 450 m at this speed? 2. Relevant equations (Eout/Ein)100% Ek=1/2mv^2 Et=Ek+Eg 3. The attempt at a solution (Eout/Ein)100% 18000N x 450m/ 18000N x 21 x Ek = 12% and then I solved for energy I know this is completely wrong but i just don't understand how to do this question without having the mass... I have my unit test tomorrow and this is the only question I don't understand on the review!! PLEASE help me i'm having trouble understanding the efficiency questions, especially this one!!! I just don't know how else to attempt it!!