# Electrostatic Force between point charges

## Homework Statement

The attractive electrostatic force between the point charges 8.12×10−6C and Q has a magnitude of 0.670N when the separation between the charges is 7.26m.

Find the sign and magnitude of the charge Q.

(this is a direct cut and paste)

## Homework Equations

FQ=k((|q1||q2|)/r^2)

## The Attempt at a Solution

8.12×10−6C = (k(|q1||q2|)/(7.26m^2))

(8.12×10−6C * 7.26m^2)/(k) = (|q1||q2|)

I'm really getting stuck here, and largely because I feel like the problem reads strangely. I feel like I'm headed in the wrong direction but if they give me Q in the beginning what am I finding? If the problem doesn't read strangely I'll keep working on it sans help.

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Yeah, that's a terribly worded question.

The 8.12e-6 C is the charge of one of the charges---the 'C' is for 'coulomb,' a measure of charge. The other charge has some value 'Q' which you need to find---that's the unknown.

The resulting force is 0.67 N---'N' is for 'newton' which is a measure of force.

So F=k((|q1||q2|)/r2)

0.67 N = k((|8.12e-6 C||Q|)/(7.26m2)) solve for Q?

Make sure you square the distance, but yes -- exactly right.

Thanks so much for the help