The Rotating Hoop Launcher package shows the dynamics of a mass that is constrained to move on a rotating hoop.  The rotating hoop model is an excellent mechanical model of first- and second-order phase transitions.  Although the minimum of the potential energy curve corresponds to the bottom of the hoop at low rotation frequency, a spontaneous symmetry breaking (cusp catastrophe) occurs as the frequency is increased.  This package presents the theory and an Easy Java Simulation (Ejs) of this experiment. The package and a demonstration were presented at the NC Section of the AAPT Spring 2008 meeting by Wolfgang Christian and Ken Rathbun.

Please note that this resource requires at least version 1.5 of Java (JRE).