References:
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.  See:
"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) manual can be downloaded from the ComPADRE Open Source Physics collection and from the Ejs website.
Note:
This simulation was created by Wolfgang Christian using the Easy Java Simulations (Ejs) modeling tool. You can examine and modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu.
Information about Ejs is available at: .

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.

[b][color=blue]My input/contributions are
1. Event for ODE Evol Page is not working to my satisfaction but the codes is
[code]if(vz>0) return 1;  // particle is not falling
//if (z>0) return 1;  // if particle z is greater than 0 , do nothing
else
return z-0.0; // change 0.0 to 0.5 for z =0.5 to action[/code]
[s]note: the if z>0>) return 1; the number 0 cannot be changed to a positive number but works for negative ??[/s]


2. panel on left[/color][/b]

[color=red][b]source code
download the *.jar for using the applet on standalone without internet connection.[/b][/color]