wonderings

you are forgetting that all objects have a certain inertia, and you will lose some energy in the form of heat when one objects hits another.

of course rolling friction is way lower than the friction of like, a rubber Block so what do i know

no, i'm not forgetting anything. that's the point. if energy can be lost, why can't momentum?

edit: i think i came off a bit too standoffish here. sorry about that