Kinetic energy = (1/2) (mass) (speed)²
At 4.5 m/s, the car's KE is (500 kg) (4.5 m/s)² = 10,125 joules
At 19 m/s, the car's KE is (500 kg) (19 m/s)² = 180,500 .
During the speed-up, the car gained (180,500 - 10,125) = 170,375 joules
of kinetic energy.
Since energy can't be created, that 170,375 joules had to come
from somewhere, so that's the amount of work that had to be done
on the car in order to speed it up from 4.5 m/s to 19 m/s.
