The Ejs Hard Disk Collision model displays a two-dimensional collision between two hard disks.  The two disks have the same mass and only one mass is moving at the beginning of the simulation.  The impact of the collision is offset by the impact parameter, b, which can be changed.  The center-of-mass of the two masses is also shown.  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.  

Ejs Hard Disk Collision 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_newton_HardDiskCollision.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 for Newtonian mechanics 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).