The Double Pendulum model displays the motion of a two-part pendulum and its Poincare map. A double pendulum is a simple pendulum with another pendulum attached to its end and the state of this dynamical system is specified by two angles and two angular velocities.   Because there is no friction, the double pendulum is an example of a Hamiltonian system and energy is conserved.  This EJS model simplifies the system by using equal length arms and masses.  Clicking in the Poincare section sets the initial conditions of the rotor.  The user can examine and modify this simulation if EJS is installed by right-clicking within the plot and selecting "Open EJS Model" from the pop-up menu item.  

The Double Pendulum model was created using the Easy Java Simulations (EJS) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_lagrangian_DoublePendulum.jar file will run the program if Java is installed.  EJS is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.

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