One of my homework questions goes 'A point charge of -.0000024 C is fixed in place, and a second, .0019 kg, point charge of -.0000076 C is fired toward the first point charge. When the second point charge is .800 m from the first, it is moving at 22 m/s. Find the velocity of the second point charge when it is .400m from the first point charge and the closest distance the second point charge gets to the first, ignore gravity. I set up the electric potential energy before + kinetic energy before = kinetic + electric potential energy after but I kept getting wrong answers and I'm not sure why.

Question

One of my homework questions goes 'A point charge of -.0000024 C is fixed in place, and a second, .0019 kg, point charge of -.0000076 C is fired toward the first point charge.  When the second point charge is .800 m from the first, it is moving at 22 m/s.  Find the velocity of the second point charge when it is .400m from the first point charge and the closest distance the second point charge gets to the first, ignore gravity.  I set up the electric potential energy before + kinetic energy before = kinetic + electric potential energy after but I kept getting wrong answers and I'm not sure why.