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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. 

References:

 

  • "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, (http://www.compadre.org/osp/items/detail.cfm?ID=7306).
  • 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, (http://www.compadre.org/OSP/items/detail.cfm?ID=10316).

Credits:

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: <http://www.um.es/fem/Ejs/> and in the OSP ComPADRE collection <http://www.compadre.org/OSP/>.

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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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Free Fall Model

Free Fall 3D Model


View elements are used to create the model's user interface.

Selecting View in the Ejs workspace displays the structure of the simulation's user interface as shown above. Although a small number of user interface elements, such as buttons, are important for controlling the temporal evolution of the model, the view also reveals relationships between the model and the geometric representation of the model. For example, the ball in the Free Fall simulation is represented using a red sphere. Right-clicking on the ball in the Tree of Elements and selecting the properties menu item display a table of properties.


Table of properties for the ball (Sphere 3D) in the Free Fall 3D model.

The ball (Sphere 3D) properties table establishes relationships between a ball's internal properties and the model.  For example, the table binds the ball's x, y, and z position properties to the model's x, y, and z variables.  Constants, such as 0.2 for the radius and red for the color, can also be used to set properties.  If the element's interaction is enabled, the element can execute Java code in response to mouse actions. In this example, the x and y values are set to zero within the On Drag action so that this mouse action only affects the z coordinate of the ball.  The complete On Drag code fragment can be seen by clicking on the editor icon next to the property name.

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For Teachers

Translations

Software Requirements

SoftwareRequirements

Android iOS Windows MacOS
with best with Chrome Chrome Chrome Chrome
support fullscreen? Yes. Chrome/Opera No. Firefox/ Sumsung 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

 

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