What is the Force on the +q Charge?

[leonne]

Homework Statement

Find the force on +q . there's a graph which has +q on 3d in the z axis and -2q on d in the z axis

Homework Equations

F=-1/4pie Eo (q²/(2d)²

The Attempt at a Solution

I don't understand why you need to add mirror image of the charges to find the force.
I know how to solve the problem from there.
The answer is -1/4pieEo(29q²/72d²

 

[VanOosten]

method of images would only be used if there was a conductive surface somewhere on that graph you are forgetting to tell us about

 

[leonne]

o that makes sense thanks yea it says says xy plane is grounded conductor. didnt think that matters but now i know lol