After downloading extensiblependulum.jar, please execute it by double-clicking, or typing "java -jar extensiblependulum.jar".

If the above application does not start, please install OpenJDK from adoptopenjdk.net.

Let's consider the extensible pendulum as shown in the above figure.

For , the following differential equation holds.

where and k is the stiffness.

This simulator numerically integrates the above differential equation and visualizes its dynamics.

Similarly to the double pendulum simulator, chaos can be observed for some initial conditions and parameters.