Galileo did a series of experiments to test his theories as to why objects stop moving after they have been set in motion. One of these experiments involved the use of a gradual incline and a rounded object such as a ball. In this experiment he observed that after a period the ball would eventually come to a stop even though nothing moved in front of it to halt the movement. He eventually concluded that the roughness of the incline and the ball caused friction between the two and eventually made the ball come to rest after a period. He later made the conclusion that in the absence of friction, a ball rolled on a perfectly flat surface would continue to roll indefinitely because of the lack of an outside force acting on it. This is one of the