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Homework Help: Find electric force on q3

  1. Sep 27, 2011 #1
    (x,y) axis in meters

    q1=60microC (0,1)
    q2=-34microC (2,0)
    q3=13microC (2,2)

    Fx3=? Fy3=?

    i used superposition
    F(net on 3)=F13+F23

    broke it down into x and y components
    Fx=(kq1q3/r13^2)(x/r13)
    Fy=(kq1q3/r13^2)(y/r13) - (kq2q3/r23^2)

    plugging in the numbers i got
    Fx=1.3
    Fy=-0.4

    mastering physics says its wrong, and I can't seem to figure out where I went wrong....any suggestions?
     
  2. jcsd
  3. Sep 27, 2011 #2

    SammyS

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    What did you use for r13, r23, x, and y ?

    Be careful regarding the direction of the forces.
     
  4. Sep 27, 2011 #3
    r13=sqrt(x2+y2)=sqrt(4+1)=2.2m

    r23=2m

    x=2
    y=1
     
  5. Sep 27, 2011 #4

    SammyS

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    It might be simply too much round-off error.

    (sqrt(5))2 = 5

    2.22 = 4.84
     
  6. Sep 29, 2011 #5
    the problem was i was entering 1 sig fig not 2 for Fy lol...online hw submissions.....they'll waste your time for the simplest reasons..thanks though :)))
     
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