what is the first law of motion

Newton's First Law of Motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue to move at a constant speed in a straight line unless acted upon by an unbalanced external force. This means that objects do not change their state of motion unless a force causes them to do so. The tendency of an object to resist changes in its motion is called inertia. If no net force acts on an object, it will maintain its current velocity, whether that is zero (at rest) or constant motion