Final answer:
In the absence of a net external force, an object at rest stays at rest and an object in motion continues to move at a constant velocity, in line with Newton's First Law of Motion, also known as the law of inertia.
Step-by-step explanation:
Newton's First Law of Motion
When no external net force acts on an object or a system of objects, two scenarios can occur according to Newton's First Law of Motion. If the object is at rest, it will remain at rest. Conversely, if the object is in motion, it will continue to move with a constant velocity.
This behavior reflects the concept of inertia, which is the tendency of an object to maintain its state of rest or uniform motion. Inertia is intrinsically linked to an object's mass. Therefore, in the absence of a net external force, an object will neither accelerate nor decelerate but will continue in its current state, whether that is at rest (scenario 1) or in uniform motion (scenario 2).