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Planetary Motion

  • Thread starter myoplex11
  • Start date
1. The problem statement, all variables and given/known data
The sun rotates around the center of the milky way galaxy at a distance of about 30,000 light years (1ly= 9.5*10^15m). if it takes about 200 million years to make one rotation, estimate the mass of our galaxy. Assume that the mass distribution of galaxy is concentrated mostly in a central uniform sphere.

2. Relevant equations

G Msun Mgalamy / r^2 = Mgalaxy v^2/ r

3. The attempt at a solution
r= (30000 * (9.5 * 10^5) ) m
v= 2 * pi * r / 200 million years
i know i have to convert the years into seconds is my setup right?


Science Advisor
Homework Helper
You have the equations slighty wrong. Your's would cancel the mass of the galaxy leaving only the mass of the sun.

And yes - you should work in m/kg/s
i am not sure what equation to use

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