# The Sun's Net Gravitational Force

1. Oct 14, 2009

### crazuiee

1. The problem statement, all variables and given/known data
The milky way galaxy ( which includes the Sun) rotates about its center with a period of 200 million years. The Sun is 2X10^20m from the center of the galaxy.

What is the net gravitational force on the sun due to the other stars in the milky way galaxy?

2. Relevant equations
F= m*a
F=Gm1m2/r^2
a=v^2/r

3. The attempt at a solution
I'm not even sure where to begin...

2. Oct 14, 2009

### Delphi51

You are given the period for the Earth's orbit around the galaxy. Can you convert that into a speed so you can use
F = m*a = m*v^2/r?
This is the centripetal force necessary to hold the Earth in its orbit, and we know that force is provided by the gravitational force so that will be your final answer.

3. Oct 14, 2009

### crazuiee

Well this is about the Sun, I think I figured it out by finding the radial acceleration, and then plugging it into the F= m*a

4. Oct 15, 2009

### stp83

Problem from College Physics text, 3rd Ed., Giambattista, Richardson, and Richardson?