Negatively charged particle is released from rest at point b and accelerates until it reaches point a. the mass and charge of the particle are 4.0 106 kg and 2.0 105 c, respectively. only the gravitational force and the electrostatic force act on the particle, which moves on a horizontal straight line without rotating. the electric potential at a is 36 v greater than that at b; in other words, va vb 36 v. what is the translational speed of the particle at point a?