find force on the +q charge

[leonne]

1. The problem statement, all variables and given/known data
Find the force on +q . Theres a graph which has +q on 3d in the z axis and -2q on d in the z axis


2. Relevant equations
F=-1/4pie Eo (q2/(2d)2


3. 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