Find the electric field at the point given

[xxabr]

Homework Statement

Find the electric field at the point given, x.

(+50uC)-------0.45m---- (-10uC) -----0.30m----- ( x )

Homework Equations

E= kq/r^2

Maybe, E= Fe/q and Fe= kq1q2/r^2

The Attempt at a Solution

q1= 50x10^-6
q2= -10x10^-6
q3= ?

I have no idea what equation to start with or where to start.
If I were to use E=kq/r^2
I don't know which charge to use for 'q'
Please help, thanks.

 

[zorro]

Use vector addition of Electric field intensity.
The electric Field at x will be
Ex = E1 + E2
where E1 and E2 are the electric field intensity vectors due to 50 and -10uc resp.

 

[xxabr]

Alright so,
If I use E=kq/r^2 for 50x10^-6C ... R would be 0.45m
and for -10x10^-6C ... R would be 0.30m?

 

[zorro]

Alright so,
If I use E=kq/r^2 for 50x10^-6C ... R would be 0.45m
and for -10x10^-6C ... R would be 0.30m?

No and Yes.
Check your book where you derived electric field intensity due to a point charge. Find out what was 'r' there