What are the magnitude and direction of the net gravitational forces acting on each of the three particles?

Question

The drawing shows three particles far away from any other objects and located on a straight line. The masses of these particles are mA = 363 kg, mB = 517 kg, and mC = 154 kg. Find the magnitude and direction of the net gravitational force acting on each of the three particles (let the direction to the right be positive).

http://i240.photobucket.com/albums/ff278/mysterypenguin12/111-1.gif

Answer 1

Each pair of particles experiences |F| = Gm1m2/r^2. The rightmost particle of the pair experiences -F and the other +F. Each of the 3 particles experiences an F from each of the other two particles. So compute the 6 pairwise Fs and for each of the 3 particles add the two Fs it experiences.