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 momenta 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.