Phsyics
posted by g .
Determine the magnitude and direction of the gravitational force exerted a) on the Moon by Earth and b) on Earth by Moon.

The forces are the same, but in opposite directions. The Earth pulls the moon and vice versa.
The force is G*M*m/R^2
G = universaL constant of gravity
m = lunar mass
M = Earth mass
R = earthmoon separation
The force also equals m*V^2/R
where V is the velocity of the moon its orbit. 
I did not get the answer...