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7.1.5 Example (N09/I/16) Binary Stars 

Two stars of mass M and 2M, at a distance 3x apart, rotate in circles about their common centre of mass O.
The gravitational force acting on the stars can be written as $\genfrac{}{}{0.1ex}{}{kG{M}^2}{x^2}$ .
What is the value of k?
A  0.22             B  0.50                C  0.67             D  2.0

7.1.5.1 Model: You may view the movement of the two stars using the EJSS below link (require internet) or just below:

1. Run Sim
2. http://iwant2study.org/ospsg/index.php/53

Answer is $\left|F\right|=G\genfrac{}{}{0.1ex}{}{M_1{M}_2}{r^2}=G\genfrac{}{}{0.1ex}{}{2MM}{{\left(3x\right)}^2}=\genfrac{}{}{0.1ex}{}{2}{9}G\genfrac{}{}{0.1ex}{}{M^2}{{\left(x\right)}^2}$

 

Translations

Code	Language		Translator	Run

Credits

Fu-Kwun Hwang - Dept. of Physics,National Taiwan normal Univ.; Loo Kang Wee; Wolfgang Christian

http://iwant2study.org/lookangejss/02_newtonianmechanics_7gravity/ejss_model_gravity02_1/gravity02_1_Simulation.xhtml

 App

• gravity02_1.apk

Versions

1. http://weelookang.blogspot.sg/2016/07/binary-stars-javascript-model-by-fu.html

Other resources

1. https://phet.colorado.edu/sims/my-solar-system/my-solar-system_en.html

 

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