A 1200kg car goes a distance of 12 meters on a road, going from 4m/s to 18 m/s in 6 seconds. If 75,000J of energy is used as heat energy, calculate power in/out and efficiency. I believe I found the correct power output, by doing (.5)(1200)(14^2)/6 = 19600W, but I dont know how to find the power input. Would I just add in the energy lost to friction to the power output? I tried this (19600W /32100W * 100% = 61%) but according to the answer book this is the wrong answer.