APS Excellence in Physics Education Award
November 2019

Science SPORE Prize
November 2011

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

## Computer Program Detail Page

Two-Body Orbits JS Model
written by Wolfgang Christian
The Two-Body Orbits JavaScript Model shows the motion of two objects (e.g., binary star or moon-planet system) interacting via Newton's law of universal gravitation.  It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.

The Two-Body Orbits JS Model was developed using the Easy Java Simulations (EJS) version 5.  Although EJS 5 is a Java program, it can create stand alone JavaScript programs that run in almost any PC or tablet browser.
1 source code document is available
Subjects Levels Resource Types
Classical Mechanics
- Gravity
= Kepler's Laws
= Orbits
= Universal Gravitation
- Motion in Two Dimensions
Mathematical Tools
- Differential Equations
- Middle School
- High School
- Instructional Material
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- Educators
- text/html
- application/zip
- application/javascript
• Currently 5.0/5

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Access Rights:
Free access
This material is released under a Creative Commons Attribution-Noncommercial-No derivatives 3.0 license.
Rights Holder:
Wolfgang Christian
Record Cloner:
Metadata instance created September 4, 2013 by Wolfgang Christian
Record Updated:
February 1, 2021 by Wolfgang Christian
Last Update
when Cataloged:
September 4, 2013

### Error in speed?

Author: Kristen Larson
Posted: January 31, 2021 at 5:28PM

I think that there is a factor of 2 error in the speed.  Two 0.5 m_sun stars separated by a = 1 AU in circular orbits should have orbital speeds of pi AU/year, not 2pi AU/year.

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ComPADRE is beta testing Citation Styles!

AIP Format
W. Christian, Computer Program TWO-BODY ORBITS JS MODEL, Version 1.0 (2013), WWW Document, (https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573).
AJP/PRST-PER
W. Christian, Computer Program TWO-BODY ORBITS JS MODEL, Version 1.0 (2013), <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573>.
APA Format
Christian, W. (2013). Two-Body Orbits JS Model (Version 1.0) [Computer software]. Retrieved May 30, 2023, from https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573
Chicago Format
Christian, Wolfgang. "Two-Body Orbits JS Model." Version 1.0. https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573 (accessed 30 May 2023).
MLA Format
Christian, Wolfgang. Two-Body Orbits JS Model. Vers. 1.0. Computer software. 2013. 30 May 2023 <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573>.
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@misc{ Author = "Wolfgang Christian", Title = {Two-Body Orbits JS Model}, Month = {September}, Year = {2013} }
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%A Wolfgang Christian %T Two-Body Orbits JS Model %D September 4, 2013 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573 %O 1.0 %O text/html

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%0 Computer Program %A Christian, Wolfgang %D September 4, 2013 %T Two-Body Orbits JS Model %7 1.0 %8 September 4, 2013 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=12996&DocID=3573

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### Two-Body Orbits JS Model:

Is the Basis For EJSS Two Body Circular Orbits Model

added the invisible mass for which the binary system's motion are derived from.
added the velocities v1x, v1y and v2x v2y
added units labels clearly showing units a.u. and year
added combo drop-down list for ease of use
added numerical values for sense making such as F1, F2, a1, a2, R1 and R2 v1 and v2
made forces a bit longer to see more clearly

relation by wee lookang
Is Based On Easy Java Simulations Modeling and Authoring Tool

Use the Easy Java Simulations Modeling and Authoring Tool to edit and to explore the source code for the Two-Body Orbits JS Model.

relation by Lyle Barbato

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