Peter Selinger: Double Pendulum

Double Pendulum

This is the same double pendulum as before, but this time the outer mass leaves a trace on the canvas. You can turn the trace on and off by using the designated button. You can also change the physical parameters of the system by clicking on the button that says "Change Parameters". A window will pop up in which you can change the values of the two masses, the lengths of the two legs of the pendulum, and the amount of gravity. When you press "enter" or click the "Apply" button, your changes will be applied. The energy of the system will be recalculated, and if necessary, the scale will change, too.

You can also change the total energy of the system. The total energy is the sum of potential and kinetic energy. The potential energy can be positive or negative, but the kinetic energy must always be positive. Thus, the Applet will not allow you to set the total energy below the current value of the potential energy.

Your browser does not run this applet, for some reason.
Here is what it would look like:

You can change the number of frames per second of the simulation. Many implementations of Java cannot gracefully handle much more than, say, 20 frames per second. Changing the rate of frames per second does not change the perceived speed of the simulation; it simply changes the number of intermediate values calculated. The simulation will still proceed in real time. If you want to see the simulation in slow or in fast motion, you can change the "time factor": a number greater than 1 means fast motion, and a number less than 1 means slow motion. You can even enter a negative time factor to see the simulation move backwards in time.

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Peter Selinger / Department of Mathematics and Statistics / Dalhousie University
selinger@mathstat.dal.ca / PGP key

Updated May 12, 2000