I am wondering how you would exactly calculate the velocity change in an object that changes mass for whatever reason, such as a rocket leaving behind parts of itself. Is this a simple case of m1v1 = m2v2, thus leaving the momentum the same as mass changes, or is the derivation more complicated?
Like, another example, lets say, hypothetically, an object was flying and suddenly just lost a bunch of mass without deformation, by magic or something. Would the velocity just change to be equal to jv, where j is some factor in which m is decreased (1/j m * jv).
The reason I am confused is that the wikipedia page lists them as separate derivations, it does not explain that well. And also the fact that it means that a change in velocity would change mass, which does not seem reasonable, as we don't see this in reality as far as I am aware. It seems as if my interpretation of the Conservation of Momentum is somehow wrong.
Could you please correct me where I am mistaken and, if it exists, show a more accurate way to calculate the momentum of a system with variable mass?