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!

Coulombs Law find q (charge)

  1. Sep 23, 2006 #1
    I attached my message and the problem in a Word document because I don't know how to enter equations in this text box.

    Thanks for your help

    Attached Files:

  2. jcsd
  3. Sep 23, 2006 #2
    Yeah your working is generally fine.

    You can assign q4 a value, but it doesn't matter since it is a common factor throughout the whole equation. So what you do is you divide the LHS and RHS of your equation by q4. This leaves:

    [tex]\frac {kq_4q_1} {q_4 (r_1_4)^2} - \frac {kq_4q_2} {q_4 (r_2_4)^2} + \frac {kq_4q_3} {q_4(r_3_4)^2} = 0/q4[/tex]

    ie [tex]\frac {kq_1} {(r_1_4)^2} - \frac {kq_2} {(r_2_4)^2} + \frac {kq_3} {(r_3_4)^2} = 0 [/tex]

    Anyway even doing it your way you should have got the same value as me, but you didn't. I got something closer to -4*10^-5 C (this isn't the answer). The actual answer is slighty more than -4*10^-5 C. So you must have made a simple calculating error.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook