# Homework Help: Moon and Sun Gravitation

1. Mar 11, 2010

### dluv

Hello! I came across this website on my quest to find an answer to this physics problem. I read a topic that was a similar problem, but it didn't address my question in particular. So now I'm posting my problem specifically, and thank you in advance for any help!

1. The problem statement, all variables and given/known data
a. What is the gravitational force on the Moon from the Sun?
b. What is the gravitational force on the Sun from the Moon?
Use 1AU as distance between the Moon and Sun.

Msun = 1.989 x 10^30 kg
Mmoon = 7.35 x 10^22 kg
1AU = 1.4960 x 10^11 m
G = 6.67 x 10^-11

2. Relevant equations

$$F = \frac{G M_1 M_2}{R^2}$$

3. The attempt at a solution

When using the above equation, I am only able to get the TOTAL gravitational force between objects, not the force of one on the other.

Is there another equation I must use or is there some way to rearrange the variables to get what I want?

2. Mar 11, 2010

### DaveC426913

$$F_m_1 = \frac{Gm_2}{r^2}$$

Last edited: Mar 11, 2010
3. Mar 11, 2010

### Stonebridge

The force of the Sun on the Moon is equal to the force of the Moon on the Sun, and that force is given by the equation you quote.
The equation is saying that the force is mutual (double ended) as in Newton's 3rd Law of Motion.