[SOLVED] Electric field and force ... 1. The problem statement, all variables and given/known data We have 2 identical thin rods , each has a length of 2a and carry a charge of +Q , uniformly distributed along their lengths , and both lie on the horizontal X-axis , and the distance between their centers is "b" ... I need to calculate the electric field and the magnitude of the force exerted by the left rod on the right one. 2. Relevant equations I know that F=Q*E and the electric field done by a charged rod on a point in its axis is E= K*Q/d(d+L) where L is the length of the rod , and d is the distance between the rod and the point. 3. The attempt at a solution Well I didn't know how to start :S , no need for a full solution , I just need a push and tell me how to start to solve it .. thanks.