Three charges in a line ( fast -please? (thanks))

[mujadeo]

three charges in a line (need help fast --please? (thanks))

Homework Statement

Two charges Qc and -Qc(Qc = 6 µC) are fixed on the x-axis at x = -8 cm andx = 8 cm, respectively. A third charge Qb = 2 µC is fixed at the origin. (attached .gif file shows the diagram)

A particle with charge q = 0.4 µC and mass m = 6 g is placed on the y-axis at y = 10 cm and released. There is no gravity.

Calculate the initial acceleration of the particle.

Homework Equations

I calculated the y component of the acceleration no prob. (asuby = 120m/s/s)

Im saying the x acceleration is zero, because all the acceleration is along the y-axis.
this is wrong for some reason?

Please help thanks!

The Attempt at a Solution

 

[Hootenanny]

Take note of the the signs of the two charges placed at (-8,0) and (8,0); one charge is Qc [i.e. positive] and the other is -Qc [i.e. negative]...