The 1st law explains that an object is at rest or in motion stays at rest or in motion unless acted on by an outside force. It also means that the object? It’s motion has a velocity unless there is an unbalanced force. The 1st law is known as the law of inertia. If there is no net force on an unbalanced object it will stay at a constant velocity. For example, if there were two cars on the road in front of each other and they hit, they move back because there is an outside force that hit them. If an object has a net force of zero the object is at rest and if not zero it is in motion. An unbalanced force acts on an object: it slows down or it stops and moves the way of the object.