In the predominant approach in physics textbooks, the collision between particles is treated as a
black box, where no physical quantity can be measured. This approach becomes even more evident in
experimental classes where collisions are the simplest and most common way of applying the theorem
of conservation of linear momentum in the asymptotic behavior. In this paper we develop and analyse
an experiment on collisions using only two smartphones. The experimental setup is amazingly simple;
the two devices are aligned on a horizontal table of lacquered wood, in order to slide more easily.
At the edge of one of them a piece of common sponge is glued using double-sided tape. By using a
free smartphone application, the values generated by the accelerometer of the two devices in full
motion are measured and tabulated. Through numerical iteration, the speed graphs of the smartphones
before, during, and after the collision are obtained. The main conclusions were: (i) the
demonstration …