Electric Field Halfway Between Two Charges

[Xet]

Homework Statement

q1 (-6.5E-7 C) @ 6 cm to the right of origin (X,Y coordinate is 6,0)
q2 (6.5E-7 C) @ 21 cm to the left of origin (X,Y coordinate is -21,0)

At the half-way point of these two charges, what is the E field value...?

Homework Equations

sum of electric fields
electric field at point is equal to constant times the charge, all divided by radius squared
constant is 8.99E9 Nmm/(CC)

The Attempt at a Solution

I found the two E's from the point to the half-way mark...I'm suppose to add the two E's because it's going from negative to positive...right? Well...I got it wrong...

 

[kdv]

Homework Statement

q1 (-6.5E-7 C) @ 6 cm to the right of origin (X,Y coordinate is 6,0)
q2 (6.5E-7 C) @ 21 cm to the left of origin (X,Y coordinate is -21,0)

At the half-way point of these two charges, what is the E field value...?

Homework Equations

sum of electric fields
electric field at point is equal to constant times the charge, all divided by radius squared
constant is 8.99E9 Nmm/(CC)

The Attempt at a Solution

I found the two E's from the point to the half-way mark...I'm suppose to add the two E's because it's going from negative to positive...right? Well...I got it wrong...

What did you use for the distance when you calculated the E field?

 

[Xet]

What did you use for the distance when you calculated the E field?

Rather dumb question to ask...but I used .135 m as R.

 

[hage567]

Rather dumb question to ask...but I used .135 m as R.

It is not a dumb question at all. You didn't show your work. How can we tell you what you did wrong if you don't show any calculations?

 

[kdv]

Rather dumb question to ask...but I used .135 m as R.

well, if it's a dumb question to ask I won't ask any question anymore.

Best luck