1. The problem statement, all variables and given/known data Two identical particles, each having charge +q, are fixed in space and separated by a distance d. A third particle with charge -Q is free to move and lies initially at rest on the perpendicular bisector of the two fixed charges a distance x from the midpoint between the two fixed charges. See image. a) Show that if x is small compared with d, the motion of -Q is simple harmonic along the perpendicular bisector. Determine the period of that motion. T=? b) How fast will the charge -Q be moving when it is at the midpoint between the two fixed charges if initially it is released at a distance a<<d from the midpoint? v_max=? 2. Relevant equations I know Coulomb's Law and Hooke's law might be used somehow, but that's about where I am. 3. The attempt at a solution I really don't even know where to start.