1. The problem statement, all variables and given/known data http://img155.imageshack.us/img155/5661/q2gf2.jpg [Broken] 3. The attempt at a solution I got the first part of the question correct but for some reason I can't get the second one. I know I did it correctly but its not working. All the forces acting on particle 2 are from particle 1, 3, and 4. I calculated the forces and added them up but I still am not getting the right answer. I tried both negative and positive answer for the same number and still it says I am wrong.