# Find equilibruium position for charged partical problem

1. Sep 18, 2006

### FocusedWolf

Find equilibrium position for charged particle problem

3 charged particles on y axis. A third particle is somewhere such that the resultant force on it is zero.

What is distance from 0rigin of x y axis to Q 3.

Node: for partical 3, thats the absolute value of 3 microcolumbs (not 131, those are absolute value things :P)... i'm assuming it's positive for this.

So I drew up a free body diagram for Forces on 3 net.

So,

Ok so how do I figure out which is the correct value of y?

[their are 3 image above...if you cant see them, then it'll look like i didn't do any work]

Last edited by a moderator: May 2, 2017
2. Sep 18, 2006

### Staff: Mentor

What range of values for y makes sense?

3. Sep 18, 2006

### FocusedWolf

i'd say above Q1...so distance from y axis =

2m + 5.84992=7.84992 or
2m + 2.29823=4.29823

hmm...unless... it's that distance (5.84992 or 2.29823) below q1 and under q2... that makes more sense.

so

2m - 5.84992=-3.84992 or
2m - 2.29823=-0.29823

below q1

Last edited: Sep 18, 2006
4. Sep 18, 2006

### Staff: Mentor

Before you even start "turning the crank" on a problem such as this, first ask yourself: What region must the 3rd charge be in? There are three choices:
(1) Above Q1
(2) Between Q1 and Q2
(3) Below Q2
Only one region allows for the possibility of equilibrium. Which? (Think it through. Imagine that the third charge is a negative charge.) Once you figure out which region Q3 must be in, then you'll know which answer is correct.

5. Sep 20, 2006

### FocusedWolf

I figured it out...only took a few days :rofl:

Q3 is the negative charge between q1 and q2.