# Columb's law Problem

1. Jan 11, 2014

### jfusion

1. The problem statement, all variables and given/known data
Charge q2 in the figure(Figure 1) is in static equilibrium. Assume that q = 4.4nC .

Figure:http://session.masteringphysics.com/myct/itemView?assignmentProblemID=31833513&offset=prev

what is q1 ( distance between q2 and q is 10com and distance between q1 and q2 is 20cm)
2. Relevant equations
F=k*q1*q2/(2d)^2 + k*q*q2/d^2 = 0

I then isolate for q1
3. The attempt at a solution
My answer is 1.7x10^-8 C which is wrong, I have converted all givens to Standard units

2. Jan 11, 2014

### vela

Staff Emeritus

3. Jan 11, 2014

### jfusion

Thanks for pointing that out, heres the image

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4. Jan 11, 2014

### vela

Staff Emeritus
Maybe it's just a matter of rounding or sig figs.

5. Jan 12, 2014

### jfusion

i don't believe so, do you come to the same conclusion?

6. Jan 13, 2014

### vela

Staff Emeritus
Yes, but when I round to two sig figs, I get a slightly different answer. Also, it could be that you didn't specify the correct sign of the charge.

7. Jan 13, 2014

### jfusion

what do get as your final answer? and the charge would be + correct?

8. Jan 13, 2014

### jfusion

it accepted 16nC thanks for the help