Electric charges and conservation of energy

[vex390]

Homework Statement

Two charged particles connected by a string exert electric forces on one another. One has a mass of 3 grams and the other 6 grams. The string is .04m. The force is calculated to be 50.56N. What is the tension in the string? What is the total energy of the system?

Homework Equations

Newton's laws.
Conservation of Energy.

The Attempt at a Solution

The sum force on each particle is 50.56N, making the tension out to be T = 50.56N.

I calculated the potential energy to be U = 2.022J from earlier in the problem.

The part that I'm stuck on is getting the final velocities.

U(i) - U(f) = k(f) - k(i)

2.022 = k(f)

So I set up the equation as:
2.022 = (1/2)(.003)(v$_{}1$^2) + (1/2)(.006)(v$_{}2$^2)

is that right? How would I find 2 different velocities from that? Or are the velocities different?

 

[vex390]

Should I use conservation of momentum to find the velocities?