  We show the value of mass-momentum diagrams for analyzing collision problems
in classical mechanics in one dimension. Collisions are characterized by the
coefficient of restitution and the momentum of the interacting particles both
before and after the collision. All those quantities are presented in the
mass-momentum diagrams without the need to do any calculations. We also show
that the same diagrams can be used to investigate collisions with respect to
the center-of-mass system. In this case, also, we do not need to do any
calculations to obtain the momentum. Since we give an alternative way of
looking at collisions in classical mechanics, this article is aimed at
undergraduate-level students.
