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Homework Help: Charged particles - magnitude of force

  1. Jan 30, 2006 #1
    http://img77.imageshack.us/img77/5310/chargedparticles7of.png [Broken]

    What is the magnitude of the force on a
    -1.2 muC charge placed at a point 1.6 cm to the left of the
    middle charge?? Answer in units of N.

    This is what I did:

    I used Fx = k*|Q|*(qx/r^2)

    Q= 1.2*E-6

    I plugged in 8.6*E-6 into the above equation (keep in mind i used 3.7cm-1.6cm =2.1 cm --> .021m) and got F1=210.320898

    I plugged in 4*E-6 into the above equation (i used .016m) and got F2=168.5165625

    I plugged in -1.2*E-6 into the above equation (i used .016+.032=.048m) and got F3 = -5.61721875

    Then for F final = -F1 + F2 - F3 = -36.187

    Since it asks for magnitude I plugged in 36.187. It came up as wrong... where did i go wrong??
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Jan 31, 2006 #2
    It would be great if someone can offer any help within the next 3 hours.
  4. Jan 31, 2006 #3
    According to the way you've defined F1, F2 and F3, your net force should be

    Fnet = -F1 + F2 + F3

    which comes out as 47 something newtons.
  5. Jan 31, 2006 #4
    Wow, that was it. Thanks A LOT!!!! People like you make this site awesome. Thanks again. :approve:
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