Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This tendency to resist changes in a state of motion is inertia. If all the external forces cancel each other out, then there is no net force acting on the object. If all the external forces cancel each other out, then there is no net force acting on the object.  If there is no net force acting on the object, then the object will maintain a constant velocity.