# Size of Force between two Point Charges

1. Apr 17, 2010

### ZedCar

1. The problem statement, all variables and given/known data
A point charge of +2.0 microC is separated from a second point charge of -0.35 microC by a distance of 4.0 x10-4 m. Calculate the size of the force that each charge exerts on the other and its direction. (Assume 1/4 pi ε0 = 9.0 x109 m F-1)

2. Relevant equations

F = 1/(4 pi ε0) x (q1 x q2 / r-squared)

3. The attempt at a solution

I get an answer of -3.9 x 10 (power of 4) N

The question asks for the direction. So by stating the -'ve before the 3.9 am I indicating the direction?

Or should I state the answer is +3.9 x 10 (power of 4) N in a particular direction?

Thank you

2. Apr 17, 2010

### Cryxic

You've got the size of the force down. As for the direction: you have opposite charges, which means they attract one another. So your first answer (the negative one) is the one you should use.

3. Apr 17, 2010

### ZedCar

Ok, thanks very much for the help Cryxic. It's very much appreciated.