Newton's first law of motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced external force. Specifically, it explains that an object's state of motion will remain constant unless an outside force causes its speed or direction to change. Examples given are that a ball in flight would never stop without forces like gravity and friction, and a golf ball on a tee would sit there indefinitely without an external force making it move.