Newton's Three Laws of Motion

Newton's First Law of Motion is also known as the law of inertia. The concept of inertia was introduced before Newton by Galileo and Descartes, but Newton refined and expanded it. The law states that objects will not change their state of motion (either at rest or in uniform motion) unless a force is applied. This force must be unbalanced, meaning there is a net force acting on the object. If the forces acting on an object are balanced, the object will either remain stationary or continue moving at a constant velocity.
The key concept in this law is inertia, which is the tendency of objects to resist changes in their motion. Every object has a natural state of motion, and it is only external forces that can alter this state.