Calculating Electric Field at 0.8m from Charges on x-Axis

[soul5]

Homework Statement

A charge of 3.5*10^-6 is fixed on the x-axis at x= 0.55m, while a charge of -15*10^-6 is fixed at the origin. What is the net electric field on the x-axis at 0.8m?

Homework Equations

Fe = qE

The Attempt at a Solution

Used Fe = qE, but that's it.

 

[tiny-tim]

Hi soul5!

How about using $$q/r^2$$?

 

[Mike Cookson]

Apply the principal of super position. The field at any point is the sum of the two individual fields at that same point when acting independently...IE work out the individual fields at x=0.55m and then add them together.