Dynamics of a Bead on a Rotating Hoop Model Documents

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Main Document

Dynamics on a Rotating Hoop 

written by Wolfgang Christian

A mass constrained to move on a rotating hoop 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.  Although the equations governing these rotating hoop models can be understood using elementary mechanics, they can be used to illustrate advanced concepts such as symmetry breaking and phase transitions.

The Dynamics on a Rotating Hoop model was created using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double click the ejs_mech_lagrangian_RotatingOffAxisHoop.jar file to run the program if Java is installed.

Last Modified January 19, 2012

This file has previous versions.

Supplemental Documents

Rotating On Axis Hoop 

A simplified version of the off-axis Dynamics on a Rotating Hoop model.

Last Modified January 19, 2012

This file has previous versions.

Source Code Documents

Dynamics on a Rotating Hoop Source Code 

The source code zip archive contains an XML representation of off-axis and on-axis Dynamics on a Rotating Hoop models.   Unzip this archive in your EJS workspace to compile and run this model using EJS.

Last Modified September 2, 2009