Question

Action and reaction forces do not balance each other. Why?

Answer 1

Although action and reaction forces are always equal and opposite to each other, they are acting on two different objects. Saying that the forces balance each other implies that they are adding up to equal zero. Forces are only added when they are acting on the same object, not on different objects. If you are looking at the motion of a car, you are interested in the forces that are acting ON the car, but not on any forces that the car is exerting on other objects. That would affect the motion of the other objects, but not the motion of the car.