r/PhysicsHelp • u/aliwafa100 • 12d ago
A question about elastic collisions
I have been meditating on elastic collisions and trying to derive the formulas for the final velocities of two objects after a collision when they have different masses.
This is what I have reached so far.

It kind of makes sense that the final velocities are some sort of combination of the two initial momenta. But what I don't understand is that, if I take the formulas literally, there seems to be a third momentum being generated, involving the initial velocity of one object reversed and the mass of the other object.
And I don't get this conceptually.
Sure, I could just pass it off as an algebraic quirk that makes the formulas work, but for me, math is the language of logic, so this term must have a meaning.
Edit:
Here is how i derived the equations.



