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: Electricity and charge question, equilibrium, help!

  1. Aug 31, 2008 #1
    1. The problem statement, all variables and given/known data

    a charge of q is fixed on a plane at the origin of an xy coordinate system and a charge 3q is fixed at (3cm, -3cm). where must a charge of -2q be placed at rest for it to be in equilibrium so that it remains at rest? is the equilibrium stable?

    2. Relevant equations

    coulomb's law

    3. The attempt at a solution
  2. jcsd
  3. Sep 1, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi briteliner! Welcome to PF! :smile:

    How far have you got?

    Can you work out what line it must be on, and whether it's between or outside the charges? :smile:
  4. Sep 1, 2008 #3
    i don't really know where to start, all i know is that since the -2q charge is negative it should be in between the charges. i think?
  5. Sep 1, 2008 #4


    User Avatar
    Science Advisor
    Homework Helper

    Hi briteliner! :smile:

    Yes, it is repelled by both the other charges, and so it must be between them.

    ok … there's a line joining the two other charges … which side of that line must the third charge be on? :smile:
  6. Sep 1, 2008 #5
    why would it make a difference which side it is on?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook