1. Not finding help here? Sign up for a free 30min 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!

Magnitude and direction of net force acting on a charge.

  1. Sep 27, 2012 #1
    1. The problem statement, all variables and given/known data
    Four charges,
    q1 = +195 µC, q2 = +60 µC, q3 = −145 µC, and q4 = +21 µC,
    are fixed at the corners of a 4 m by 5 m rectangle, as illustrated in the figure below. What are the magnitude and the direction of the net force acting on q1? (Assume the x-axis extends from q1 to the right.)

    q3--------------------q2
    | |
    | |
    | |
    q4--------------------q1

    2. Relevant equations

    F = k q1q2/r2

    3. The attempt at a solution
    I have followed the steps outlined here. http://dev.physicslab.org/Document....lectrostatics_AdvancedCoulombsLawProblems.xml

    For Fq1q2 I get 26.30N
    Fq1q4 I get 5.89N
    and for Fq1q3 I get 24.82

    I proceed to chart it as shown F X Y
    q1q2 0 -26.30
    q1q4 5.89 0
    q1q3 24.82cos135°=-17.55 24.82sin135°=17.55
    -11.66 8.75

    Then F = sqr.rt(-11.66)^2+(8.75)^2
    =14.58

    Then a=tan-1|8.75 /-11.66|
    =-36.89
    θ=180-36.89
    =143.11°

    Neither of which are the proper answers apparently. What am I doing wrong? Any help would be greatly appreciated.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 27, 2012 #2
    Rectangle is 4 by 5, so diagonal is not at 45o angle
     
  4. Sep 28, 2012 #3

    ehild

    User Avatar
    Homework Helper
    Gold Member

    The problems are different. Do you understand what Coulomb's Law states? What is the magnitude and the direction of a force, one charge exerts on an other one?

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook