A negative charge, -q, has a mass, m, and an initial velocity, v, but is infinitely far away from a fixed large positive charge of +Q and radius R such that if the negative charge continued at constant velocity it would miss the center of the fixec charge by a perpendicular amount b. But because of the Coulomb attraction between the two charges the incoming negative charge is deviated from its straight line course and attracted to the fixed charge and approaches it. Find the closest distance the negative charge gets to the positive one.