Final answer:
The quantity mentioned refers to momentum, which is the product of an object's mass and velocity and is conserved in the absence of external forces.
Step-by-step explanation:
The quantity is a product of the object's mass and net external force. In the absence of outside forces, it is always conserved. Mass is a measure of the total quantity of matter in an object, and it is measured in kilograms.
The net external force is the vector sum of all external forces acting on an object or system.
The interaction of mass and force plays a significant role in determining the behavior of objects as described by Newton's first law of motion, stating that in the absence of a net external force, an object at rest remains at rest, and an object in motion continues to move at a constant velocity.