gravity02_1

### 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:

Answer is $|F|=G\genfrac{}{}{0.1ex}{}{{M}_{1}{M}_{2}}{{r}^{2}}=G\genfrac{}{}{0.1ex}{}{2MM}{{\left(3x\right)}^{2}}=\genfrac{}{}{0.1ex}{}{2}{9}G\genfrac{}{}{0.1ex}{}{{M}^{2}}{{\left(x\right)}^{2}}$

### Translations

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### Software Requirements

SoftwareRequirements

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### Credits

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

### end faq

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

### end faq

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