How Is Maximum Speed Calculated for Identical Charges Released Simultaneously?

[apphysicsgirl]

Homework Statement

Two identical +6x10^-6 C charges, each with a mass of 10^-6, are placed as shown in the diagram below. All coordinates are in meters.
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An identical charge is brought in slowly from far away to point P.
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All three charges are released simultaneously. What is the maximum speed attained by each of them?

Homework Equations

V=U/q
deltaU=-deltaK

The Attempt at a Solution

I found in one part of the question that the work that it took to bring the third charge to point P was 0.18 J. I then did 0.18=-Kf+Ki to try and solve for a velocity. I got 600 m/s, but this was incorrect. I am not sure what else to do; I feel like there is something that I am missing on how to find a velocity for EACH charge.

 

[tramar]

Not exactly sure if this is right, but I would try using:

$$\Delta K = -q\Delta V$$

The potential is not the same for all charges, since the distance varies according to:

$$V=\frac{1}{4\pi\epsilon_o}\frac{q}{r}$$

For one charge, the total potential is the sum of potentials due to the other two charges.