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: Point Charges on Equilateral Triangle - Need Geometry Help

  1. Aug 29, 2011 #1
    1. The problem statement, all variables and given/known data
    http://www.ridemtl.com [Broken]

    2. Relevant equations
    F = k(q1q2/r^2)

    3. The attempt at a solution
    I know pretty much what to do for the problem, but I cannot get the right answer. I think my issue lies within what angles I am using for the components. Because it is an equilateral triangle, all angles within that triangle are 60 deg. But when I use 60 deg to calculate the components in the x & y directions, I can't come up with the right answer.

    F of 2 on 1 = 0.0579 N
    F of 3 on 1 = 0.0358 N

    x: 0.0579 cos 60 -i, 0.0358 cos 60 +i
    y: 0.0579 sin 60 -j, 0.0358 sin 60 -j

    Sum these together and use Pythagoras for overall magnitude
    The magnitude the above produces is 0.0818 N

    I am not getting the right answer. Thus I think my problem lies in the angles I am using. Can anyone shed some light?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Aug 29, 2011 #2


    User Avatar
    Homework Helper

    Nothing wrong with what you have written so far. Could be a problem with what you haven't written.

    I would have liked to see what you thought 0.0579 sin 60 was equal to, for example.

    I would then like to see how you thought the 0.0818 came about???
    Last edited by a moderator: May 5, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook