1. The problem statement, all variables and given/known data http://img521.imageshack.us/img521/1996/physicsz.jpg [Broken] 2. Relevant equations 3. The attempt at a solution I hope the drawing is somewhat clear. How do I find the force on the charge g0 and the electric field at the origin due to the charge bar? There's barely any information given. The first λ is at 7m and the second one at 10m. And you have 2 C at the origin. I do not know how to do this. I hope somebody can help me with this.