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Free Fall 3D

Free Fall 3D

The Free Fall 3D model simulates the same physics as the 2D Free Fall model but with a 3D View of the model's data.  The ball falls with constant acceleration g=-9.8 m/s2 in the z direction.  Click-dragging on the ball changes its height but leaves its velocity unchanged.  The reset button stops the animation and sets the initial conditions to y=1.8 and vy=0.


The Free Fall 3D model is  a designed to teach EJS modeling.  Right click within the simulation to examine this model in the EJS modeling and authoring tool. 



  • "Modeling Physics with Easy Java Simulations" by Wolfgang Christian and Francisco Esquembre, The Physics Teacher, November 2007, 45 (8), pp. 475-480.
  • The Easy Java Simulations (EJS) documentation can be downloaded from the ComPADRE Open Source Physics collection. W. Christian and F. Esquembre, in Modeling Science: From Free Fall to Chaos (2008), WWW Document, (
  • A video tutorial that will help you get started using Easy Java Simulations to create computer simulations.  See: L. Engelhardt, Introduction to EJS Video Tutorial (2010), WWW Document, (


The Free Fall 3D model was created by Wolfgang Christian using version 4.3 of the Easy Java Simulations (EJS) authoring and modeling tool.  You can examine and modify a compiled EJS model if you run the program by double clicking on the model's jar file.  Right-click within the running program and select "Open EJS Model" from the pop-up menu to copy the model's XML description into EJS.  You must, of course, have EJS installed on your computer.


Information about EJS is available at: <> and in the OSP ComPADRE collection <>.

Free Fall 3D

3D Navigation

The model's 3D view has many built in features that can be accessed as the program is running.

  • Left-button click-dragging on the particle changes its position.
  • Left-button click-dragging on an empty regions rotates the view.
  • Left-button shift-click-dragging zooms in and out.
  • Left-button control-click-dragging translates (pans) the view.
  • Left-button alt-click-dragging displays a 3D cursor on the scene (if the panel is “Enabled”).

It the ‘x’, ‘y’ or ‘z’ key is pressed during a mouse action, the actions affects only this coordinate.  Note also that these actions are are modified if the 3D view is projected onto a 2D plane.

Right-clicking within a 3D view displays a popup menu as shown below.



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Software Requirements


Android iOS Windows MacOS
with best with Chrome Chrome Chrome Chrome
support full-screen? Yes. Chrome/Opera No. Firefox/ Samsung Internet Not yet Yes Yes
cannot work on some mobile browser that don't understand JavaScript such as.....
cannot work on Internet Explorer 9 and below



Wolfgang Christian; Loo Kang Wee; Francisco Esquembre

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  • Kinematics
  • Science
  • Simulations