Momentum is often referred to as "inertia in motion" because it relates to the mass of an object and its velocity, encapsulated in the formula p=mv. This term, however, is considered ambiguous and not widely accepted in scientific literature, as it does not accurately convey the concept of how difficult it is to change an object's motion. Some participants in the discussion question the validity of this phrase, suggesting it may stem from a misunderstanding of inertia and momentum. Additionally, the conversation touches on the nature of conservative forces, with participants agreeing that all fundamental forces in nature can be classified as conservative. Overall, the term "inertia in motion" lacks clarity and is not commonly used in formal discussions of physics.