I think that this problem should be easy but for some reason I don't think I really understand it.(adsbygoogle = window.adsbygoogle || []).push({});

A charge of +2q is placed at the origin and a second charge of -q is placed a x = 3cm. Where can a third charge +Q be placed so that it experiences a zero force?

I figure that F3 = F1 + F2 = k2q/x^2 - kq/(x+0.03)^2 = 0

Cancelling out and cross multiplying gives 2(x+0.03) = x^2

Therefore the eq'n is x^2 + 0.12x + 0.0018 = 0

Using the quadratic eq'n to solve I found that x = -1.8 cm or x = -10.3 cm.

Here's where I'm not sure, if they are both negative does that mean that they are to the left of the origin, and if so which is the correct one then??

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Charge Placement where Force is Zero

**Physics Forums | Science Articles, Homework Help, Discussion**