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Electric forces questions

  1. Apr 6, 2008 #1
    i was absent for a couple days and i have absolutely no idea whats going on. Help with any of the questions would be amazing.


    for #1 first i found the diagonal distance equals [tex]\sqrt{98}[/tex]
    then i used the formula F=KC x q1 x q2/ [tex]r^{2}[/tex] to find the electric force between the 8nC charge and the two others:
    8.99E9(8E-6 x 7E-6)/ 98 = 5.14E-3
    and 8.99E9(8E-6 x 2E-6)/ 98 = 1.47E-3

    after that i had no clue, except i know #4 is 0
    Last edited: Apr 7, 2008
  2. jcsd
  3. Apr 7, 2008 #2


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    Homework Helper

    Welcome to PF.

    Don't forget to include the direction when calculating the force. The formula you gave is actually a vector equation, and to get the magnitude and direction right you should add the two forces as vectors.
    Also, when writing down a final answer, include units (if they ask you to calculate force, your answer will be something like: F = ... N in the x-direction, or [itex]\vec F[N] = \cdots \hat{x}[/itex]).

    You have learned to work with vectors already, is that correct?
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