In July 2015, the 46th International Physics Olympiad was held in Mumbai, the capital city of the Indian state, Maharashtra. Members of the Czech team obtained three silver medals and two bronze medals. In addition, the Slovak team won one silver and three bronze medals. In this article a theoretical task set during the competition is presented, which deals with calculations of a nuclear fission reactor. and Filip Studnička, Jan Kříž, Ľubomír Konrád, Bohumil Vybíral.
Two theoretical problem from the International Physics Olympiad (IPhO) are presented. First of them was assigned at the 42th IPhO in 2012 in Thailand. The motivation for the problem was to describe the motion of three satelites forming together the Laser Interferometry Space Antenna (LISA), the device designed to detect gravitational waves. The second presented problem (from 45th IPhO in 2014 in Kazakhstan) concerns the simplest models of gas discharges. and Jan Kříž, Filip Studnička, Ľubomír Konrád, Bohumil Vybíral.