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The Open Source Physics Project is supported by NSF DUE-0442581.

Computer Program Detail Page

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Ejs Hard Disk Gas Model
written by Wolfgang Christian
The Ejs Hard Disk Gas model displays a two-dimensional gas made out of hard disks.  Particles are initialized with a speed v=1 in a random direction and move with constant velocity until a collision occurs.  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 Gas 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_HardDiskGas.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).
Subjects Levels Resource Types
Classical Mechanics
- Linear Momentum
= Collisions in Two Dimensions
Thermo & Stat Mech
- Models
= Ideal Gas
- Lower Undergraduate
- Upper Undergraduate
- Instructional Material
= Activity
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- Professional/Practitioners
- Educators
- application/java
  • Currently 5.0/5

Rated 5.0 stars by 2 people

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Access Rights:
Free access
© 2008 Wolfgang Christian
Additional information is available.
Easy Java Simulations, Ejs, OSP, Open Source Physics, classical mechanics, collisions, disk, gas, ideal gas, modeling, two dimensions
Record Creator:
Metadata instance created July 5, 2008 by Mario Belloni
Record Updated:
June 5, 2014 by Andreu Glasmann
Last Update
when Cataloged:
July 1, 2008
Other Collections:

great physics stuff! Ejs Hard Disk Gas Model

Author: lookang
Posted: March 18, 2010 at 5:28AM

i love Ejs Hard Disk Gas Model.
i get to learn alot from modifying the codes.

I can't say i know exactly what each line of code is doing but i am presented a way to make sense of the computational physics by changing a bit of the codes and observe what happens.

my remixed work here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1455.0 will run your collision detection codes!

I also notice it is too difficult to run 400 molecules smoothly due to the calculation of the event for 400*400 collisions possible. Will lower it to 50 molecules!

Thanks Prof Wolfgang! going to rate this 5 stars! :)

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ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
W. Christian, Computer Program EJS HARD DISK GAS MODEL, Version 1.0 (2008), WWW Document, (https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593).
W. Christian, Computer Program EJS HARD DISK GAS MODEL, Version 1.0 (2008), <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593>.
APA Format
Christian, W. (2008). Ejs Hard Disk Gas Model (Version 1.0) [Computer software]. Retrieved July 21, 2024, from https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593
Chicago Format
Christian, Wolfgang. "Ejs Hard Disk Gas Model." Version 1.0. https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593 (accessed 21 July 2024).
MLA Format
Christian, Wolfgang. Ejs Hard Disk Gas Model. Vers. 1.0. Computer software. 2008. Java (JRE) 1.5. 21 July 2024 <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593>.
BibTeX Export Format
@misc{ Author = "Wolfgang Christian", Title = {Ejs Hard Disk Gas Model}, Month = {July}, Year = {2008} }
Refer Export Format

%A Wolfgang Christian %T Ejs Hard Disk Gas Model %D July 1, 2008 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593 %O 1.0 %O application/java

EndNote Export Format

%0 Computer Program %A Christian, Wolfgang %D July 1, 2008 %T Ejs Hard Disk Gas Model %7 1.0 %8 July 1, 2008 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=7573&DocID=593

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Ejs Hard Disk Gas Model:

Is Based On Easy Java Simulations Modeling and Authoring Tool

The Easy Java Simulations Modeling and Authoring Tool is needed to explore the computational model used in the Ejs Hard Disk Gas Model.

relation by Mario Belloni
Is Based On Easy Java Simulations Modeling and Authoring Tool

The Ejs tool is needed to explore the computational model.

relation by Anne Cox
Is the Basis For http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1482.0

made changes to the model so that i can learn more about it and the changes are:

1. made n selectable by defining nmax and insert as the n maximum limit
2. made v0 selectable by changing the codes
3. made arrows array to be drawn to understand where the particles are heading
4. made text array to allow eye balling what each particle is doing
5 change some minor values to make cellSize selectable as well.
6 added e coefficient of restitution but the codes does not work well when e = 0 probably due to the collision detection codes, goes to a deep loop when too much particles are near each other.


relation by wee lookang

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