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Homework Help: How to calculate net force

  1. May 20, 2016 #1
    1. The problem statement, all variables and given/known data
    Calculate the net force on A.

    2. Relevant equations
    F=k . (q1 q2)/r^2 , k=9 x 10^9 Nm^2/C^2

    3. The attempt at a solution
    (9*10^9 Nm^2/C^2)(1,4 x 10^-6C)(7,2 x 10^-6C) / 1,7mm^2
    = 0,0313.
    Could someone tell me what I am missing even if what i did is even correct.
  2. jcsd
  3. May 20, 2016 #2
    That’s NOT how you do it!
    You add:
    F(B)=k (qA qB)/(AB)^2 and F(C)=k (qA qC)/(AC)^2
    As I said before, you ’superpose
    ’ (add) these 2 forces.
    Do you understand now?
  4. May 20, 2016 #3
    • Poster has been reminded not to do too much of the student's work for them...
    F=(9*10^9 Nm^2/C^2)(1,6 x 10^-6C)(1,4 x 10^-6C) / 1,7mm^2+(9*10^9 Nm^2/C^2)(1,6 x 10^-6C)(7,2 x 10^-6C) / 3,4mm^2
  5. May 20, 2016 #4
    Yes! I understand now. Thanks once again. you've saved me. ;)
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