The EJS Kac Model simulates the relaxation of a gas to equilibrium by randomly selecting and then colliding gas molecules but without keeping track of the molecules' positions. As long as the collisions are consistent with spatial isotropy, the Boltzmann speed distribution will emerge. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item.

The Kac 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_stp_KacModel.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.  Additional Ejs models are available.  They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

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