1. The problem statement, all variables and given/known data Hi, I'm on the first part of this question and I've got to the end but I have an extra factor of two which I can't seem to explain! Any insight would be much appreciated, thank you! 2. Relevant equations 3. The attempt at a solution I resolved the forces around one ball and came up with the following: Resolving vertically: mg = Tcosθ, Resolving horizontally: Tsinθ = F2,1 Then using pythagoras I found sinθ = r/2l and cosθ = √(4l2 - r2) Putting it all together I get: 2F2,1 = mgr/√(4l2 - r2) I just don't understand the extra factor of 2. I thought it might be because it's at half the separation but this isn't correct. Any help would be much appreciated. Thank you!