The conservation of momentum is based on which understanding?

The conservation of momentum holds true regardless of the details of an interaction because it is a fundamental principle in physics that applies to closed systems where no external forces influence the total momentum. This principle asserts that when two or more bodies interact, the total momentum of the system before the interaction will equal the total momentum after the interaction, assuming no external forces are acting on the system. This is true for all types of interactions—elastic, inelastic, or perfectly inelastic—making it a robust concept across various physical scenarios.

This foundational understanding allows us to analyze complex systems and predict outcomes based solely on the conservation laws without needing to delve into the specific forces or processes at play during the interaction. This universality is critical for simplifying problems in mechanics and ensuring that momentum conservation can be employed in diverse applications, from collisions between cars to interactions at a particle level.

In contrast, some of the other options present a more limited view of momentum conservation. For instance, focusing only on free-fall conditions or elastic collisions neglects the wide range of scenarios where momentum conservation is applicable. Moreover, defining momentum conservation merely in terms of resistance to motion change overlooks the comprehensive nature of momentum as a conserved quantity in closed systems.