A charge of -3.00uC is fixed in place. From a horizontal distance of 0.0450m, a particle of mass 7.20x10^-3 kg and charge -8uC is fired with an initial speed of 65m/s directly toward the fixed charge. How far does the particle travel before its speed is zero?
First find the kinetic energy of the fired particle, then put it equal to the Coulomb potential between the two, find the seperation, r, Bob's your uncle.