Question

Your Hummer just stalled out. Seeing how you are not going to be able to push the vehicle to the side of the road by yourself you ask your friend Keoni to give you a hand in pushing. Having just taken Physics, he tells you that he would be of no help to you. He goes on to explain that, due to Newton’s third law, when he push the car with a force the car would push back with an equal and opposite force on him. This will result in the two forces canceling out one another, making acceleration impossible. Having taken Physic yourself, you go on to convince him that this is not the case and that his help would be invaluable in moving the car. What did you say?

Answer 1

Although Newton's third law says that every action has an equal and opposite reaction, it also says that the action and reaction act on separate bodies. Thus, when he would push the car, his force of action would act on the car while the car's reaction will act on him, instead of acting on the car. If his action is greater than the car's friction with the road, the car would move. Whereas, the car's reaction on him would be balanced by the friction between his shoes and the road. Thus, he really can move the car provided he applies more force than that offered by the friction between the road and the car's tires.