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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

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

 

Credits

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

end faq