1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Size of Force between two Point Charges

  1. Apr 17, 2010 #1
    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. jcsd
  3. Apr 17, 2010 #2
    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.
  4. Apr 17, 2010 #3
    Ok, thanks very much for the help Cryxic. It's very much appreciated. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook