Balls in a Box Model Documents

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Main Document

Balls in a Box Model 

written by Wolfgang Christian

The Balls in a Box model shows that a system of particles is very sensitive to its initial conditions. In general, an isolated system of many particles that is prepared in a nonrandom configuration will change in time so as to approach its most random configuration where it is in equilibrium. This model explores what happens if the initial conditions are chosen in a very special way.

The default initial condition corresponds to eight stationary particles perfectly aligned on the x-axis. Two particles approach from the left and the right and collide with the aligned balls. The Ejs model solves Newton's second law of motion numerically, pauses when a collision is detected, applies conservation of energy and momentum to the collision, and then the simulation is resumed. Small changes in the initial conditions of the system can be made to explore the sensitivity of the motion to perturbations.

The Balls in a Box 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_sto_BallsInBox.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 classical mechanics are available.  They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Published November 15, 2008
Last Modified June 2, 2014

This file has previous versions.

Source Code Documents

Balls in a Box Model source code 

The source code zip archive contains an XML representation of the Balls in a Box Model.  Unzip this archive in your Ejs workspace to compile and run this model using Ejs.

Last Modified November 16, 2008