Vector Analysis of Point Charges: Solving for Net Force

[pat666]

Homework Statement

i think i may have solved this but I am worried I am wrong because it seemed too simple. I wouldn't bother posting too check except that its for an assignment... the question is in the attachment- can someone please check this!

Homework Equations

The Attempt at a Solution

F_1,2=(3*10^(-6)^2*9*〖10〗^9)/〖0.6〗^2
=0.225i

F_3,2=(3*10^(-6)^2*9*〖10〗^9)/〖0.3〗^2
=0.9j

F_4,2=(3*10^(-6)^2*9*10^9)/(〖0.6〗^2+〖0.3〗^2 )
=0.18cosθ+0.18 sinθ
θ=tan^(-1)〖0.3/0.6〗
F_4,2=0.161i+0.080j

ΣF=0.161i+0.225i+0.9j+0.080J
=0.386i+0.98j

 

[Ush]

that looks correct,

 

[pat666]

thanks ush - can't get the other one though