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Find the Force and Direction of a charge

  1. May 9, 2009 #1
    1. The problem statement, all variables and given/known data
    http://www.brainmass.com/homework-help/physics/electromagnetic-theory/98519
    That site has the diagram of the Lab and distances.

    Rg-r=sqrt 3.7092 + .5332 = 3.75
    Fg-r= K(q1)(q2)/Rg-r2= (8.99x109)(1x10-5)(1x10-5)/3.752 = .064
    angle 1 = tan-1(.533/3.709) = 8.18 degrees

    Rb-r=sqrt 2.5532 + 2.7092 = 3.72
    Fb-r= K(q1)(q2)/Rg-r2= (8.99x109)(1x10-5)(1x10-5)/3.722 = .065
    angle 1 = tan-1(2.533/2.709) = 43 degrees

    Fxg-r = (.064)Cosine8.18 = .063
    Fyg-r = (.064Sine8.18 = .009

    Fxb-r = (.065)Cosine43 = .048
    Fyb-r = (.065)Sine43 = .044

    Fx = .063 + .048 = .111
    Fy = .009 + .044 = .053

    Force = sqrt of .1112 + .0532 = .123N
    Angle = tan-1(.64/.65) = 45 degrees + 8.18 = 53 degrees to the + X

    The lab shows that the total Force = .185N
    Where did I go wrong?!?!
     
  2. jcsd
  3. May 9, 2009 #2

    diazona

    User Avatar
    Homework Helper

    It's kind of hard to tell, but it looks like you calculated the force on the charge at t = 0, that is, as soon as it is released. The problem is asking for the force after 1 second. To figure it out you'd have to write and solve a differential equation for the charge's position as a function of time... seems like a rather unpleasant thing to have to do :-( Are you sure you're supposed to calculate this?
     
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