The Hard Disk PVT System simulates a two-dimensional system of particles confined between a thermal reservoir and a piston.   This computer model is designed to study the equation of state for hard disks without other interactions.   Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow.  Users can set the initial particle energy, the initial particle separation, and the thermal reservoir temperature Tr.  The thermal conductivity parameter ? determines the probability that a collision with the thermal wall will affect (thermalize) the colliding particle.  If the conductivity is one, the particle velocity after a reservoir collision is set according to Maxwell-Boltzmann statistics.  If the conductivity is zero, all reservoir collisions are elastic and the internal energy E of the system is conserved.
 
Particles in this model have unit mass and interact through contact forces.  Collision times are computed analytically because particles and pistons move with constant velocity between collisions. The time evolution algorithm advances the particle and piston positions from collision to collision until the requested time step ?t is achieved.  The time evolution is then paused, data is accumulated, and the screen is redrawn.

The Hard Disk PVT model is a supplemental simulation for the article "Pressure Oscillations in Adiabatic Compression" by Roland Stout in The Physics Teacher 49(5), 280-281 (2011) and has been approved by the author and The Physics Teacher editor.  The model was developed using the Easy Java Simulations (Ejs) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the  ejs_stp_hd_HardDiskPVTSystem.jar file will run the program if Java is installed.

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