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A bungee jump is described in terms of a simple theoretical model of a small body attached to an ideally elastic massive cord. In the first phase of the jump the cord remains unstretched and the sum of the kinetic and gravitational potential energy is assumed to be constant. In the second phase of the jump the cord is stretched and the elastic potential energy of the cord has to be included. The transition between both phases is described by an inelastic collision. Zusammenfassung. Der Seilsprung wird mit einem einfachen theoretischen Modell eines kleinen Körpers an einem idealen elastischen massiven Seil erörtert. In der ersten Phase des Sprungs ist das Seil ungespannt und wird die Summe der kinetischen und potentiellen Energie als konstant angenommen. In der zweiten Phase wird das Seil gespannt und muss seine elastische Energie berüksichtigt werden. Der Übergang zwischen beiden Phasen wird mit einem inelastischen Stoss beschrieben.

This paper presents experimental and analytical work of which the main objective was to support the introduction of a new technology for the production of sewer pipes. In this technology, the pipes produced consist of two differently produced parts. The direct part uses conventional vibro press compacted concrete. In the curved part, on the other hand, self-compacting concrete technology is used. The cooperating company, Prefa Brno a.s., defined possible negative effects on concrete of sewer pipes. The task of the research team and now the author’s team was to propose a procedure for the development of suitable self-compacting concrete variants and subsequently the design of a methodology to verify their durability in aqueous environments containing sulfates. To increase the efficiency of the development, the model mortar method was used in the experimental work. That is, instead of the original concrete, a model mortar derived from it was tested. The principle and procedure of derivation of model mortars are described in the paper. In total, eight variants of model mortars were tested, and at least three of them fulfilled the requirements. An optional but beneficial part of the carried out work was the derivation and practical application of the time-anchored-triangles-of-cracking graphical method developed during the research. This method is used to quickly compare the degree of attack of different silicate composites tested in a common bath inducing type III corrosion.