Force of attraction between mars and its moon

[Irishtank]

Homework Statement

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.

Homework Equations

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

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

 

[Irishtank]

Need Help!

 

[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.

 

[Irishtank]

First time. Thanks, won't happen again.

 

[phinds]

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

 

[SteamKing]

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.

 

[gneill]

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.