You must keep money moving

Physics teachers often like to discuss physics concepts with their students on the basis of simple demonstration experiments. In this article, we discuss an experiment for which one only needs a few coins of the same denomination and a wooden stick: the coins are laid alongside the stick on a horizontal surface, the stick is rotated about one of its endpoints, and when the stick stops, the coins move away and, once they have stopped moving, the coins seem to lie on a parabola. The students' task is to validate and understand this. They will discover by video analysis that the experimental results may not be as obvious as initially thought, and that the most plausible explanation of the real phenomenon must be slightly modified to get the measurements and theory to be in agreement. This does not simply lead to a considerable amount of effort either correcting or verifying experimental flaws, but it actually gives ample opportunity to experience how the use of physics, mathematics, and technology can jointly help to achieve a good understanding of the real phenomenon.