This allowed him to discover his third and final law which is Newton's third law of motion. Newton's third law states that for every action or force there is an equal but opposite reaction. This means that if an object crashes into another object, both objects will bounce off each other. Sir Isaac Newton's third law is often proven correct because when a car accident occurs, it is proven that when cars collide with each other, the cars bounce off each other. This proves that Newton's study was accurate and will always be used in science, regardless of the number of years