If your browser is enabled for Java, the following applet will demonstrate the role of inelasticity on the velocity and density distribution of a simulated one dimensional gas. The particle on the right gets a random velocity when it collides with the right wall.

There are two relevant parameters that may be adjusted:

- The coefficient of restitution
**r**, which is the fraction of the initial kinetic energy that remains after a collision (Red bar,Drag mouse to change ). - The number of particles
**N**(Gray bar).

The particles cluster near the left wall as r is decreased. You
may also observe "inelastic collapse" (an infinite number of
collisions in finite time) for small **r**.

The theory is from Y. Du, H. Li, and L.P. Kadanoff Phys. Rev. Lett. (1995).

The program written in **Java** using
JDK 1.1. The advantage of an
applet is that it is interactive. Move the bar on the top right to
change **r**. Besides changing **r** and **N**, and the
**Reset** button, you may also stop and resume the program by
clicking on the black **background**.

Source code for the applet and program details.

Recently we have done experiments that reveal similar phenomena in a quasi-two dimensional system. See A. Kudrolli, M. Wolpert, and J.P. Gollub Phys. Rev. Lett. (1997).

Sites we found useful in developing this program:

- Some Java programs can be found here.
- comp.lang.java FAQ, contains a good introduction and summary.

For information on the program contact

Department of PhysicsHaverford College

Haverford, PA 19041

last updated 2/18/97.