Method to the Movement

The energy behind the car is the elastic potential energy in the rubber band. When it is pulled back the energy increases and when released the energy is transferred from the rubber band to the car.This force is equal and oppose of the pull which is Newton's 3rd law.The car also demonstration Newton's 1st law. Because when the unbalanced force, the rubber band acts on it it moves. It would continue to do that but because of friction and Newton's 1st law it slows to a stop when all the kinetic energy turns back into potential energy.