  The International Physicists' Tournament (IPT) 2019 dealt with 17 challenging
problems. In this article, we present experimental as well as theoretical
approaches exemplarily to one of these tasks. A ball placed on a hard and at
surface can show oscillation movement when being hit by a jet of water from
above. To explain the oscillations, a theoretical model is introduced and its
predictions are compared to the experimental measurements. Furthermore, the
structure of the IPT itself is characterized shortly in this article, as well
as the idea of a new and innovative seminar which was set up at Erlangen
University to prepare and assist students in taking part in International
Physicists' Tournament. Furthermore, the educational relevance of physics
tournaments like IPT for physics education at university is discussed in
detail.
