Newton's First Law In the 1600's, Galileo Galilei and Isaac Newton observed moving objects and thought about the nature of motion. (At that time, people thought moving objects tend to slow down and stop by themselves. They did not realize that objects slow down and stop because of friction.) Galileo and Newton realized that a moving object keeps moving as long as friction does not slow it enough to stop it. They also observed that a stationary object - one at rest - remains still unless something makes it move. The tendency for an object to resist changes in motion is called inertia. (Galileo first used the word inertia. He reasoned that a moving body would continue moving forever in the absence of an outside force.) Newton's first law of motion states that if no force acts on an object, the object will continue moving at the same speed in the same direction. If the object is stopped, it will remain at rest. This law is sometimes called the law of inertia. Click on the video below to see Newton's 1st law in action. In the opening frames of this video, what object is at rest? What is applied to this object to cause it to move? Can you identify another part of Newton's 1st Law that occurs in the video?