# Force of attraction between mars and its moon

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1. Oct 24, 2013

### Irishtank

1. The problem statement, all variables and given/known data
The force of attraction between mars and its moon, Phobos, which has a mass of 1.072 x 10^16kg and a radius of 11.1km is 5,18 x 10^15 N
Find the height of Phobos above the surface of the moon.

2. Relevant equations
f=G(m1)(m2)/d^2
d(mars-phobos surfaces)= d (moon-phobos centres) - r (moon) - r(phobos)

3. The attempt at a solution
distance between the centres of mars and phobos= 9.37 x 10^6m
radius of moon= 1.74 x10 ^6m

I don't know how they get the answer 5.95 x 10^6m

2. Oct 24, 2013

### Irishtank

Need Help!

3. Oct 24, 2013

### phinds

Bumping your thread after 2 minutes will NOT win you any friends on this forum. The rules, which you clearly have not read, say wait at least 24 HOURS, not 2 minutes.

4. Oct 24, 2013

### Irishtank

First time. Thanks, won't happen again.

5. Oct 24, 2013

### phinds

No problem. Sorry I can't help w/ your problem.

6. Oct 24, 2013

### SteamKing

Staff Emeritus
Your attempt at answering the question is unclear. Phobos is a satellite of Mars. The 'moon' is 'Phobos', at least from Mars' perspective. You have suddenly inserted earth's 'moon' into your problem. Your question is dealing only with Mars and Phobos.

7. Oct 24, 2013

### Staff: Mentor

What is the exact statement of the problem as given to you? Surely the problem can't be asking about the distance between Earth's moon and one of Mars' moons.