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Find i j k force on charge

  1. Oct 1, 2009 #1
    1. Find in the i, j, k format, the force on the +8 micro-Coulomb charge (pic att'd)

    F = 1.6 x 10^-4 N



    no clue where to start

    soa9tf.jpg

    thx
     

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    Last edited: Oct 1, 2009
  2. jcsd
  3. Oct 1, 2009 #2

    Delphi51

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    Use the formula for electric field causing a force on a charge: Fe = q*E
     
  4. Oct 1, 2009 #3
    got that. that's where the 1.6 x 10^-4 came from.
     
  5. Oct 1, 2009 #4

    Delphi51

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    Are you finished then, or do you need to add the electric field due to the other charge? A good idea to show formula and numbers - the answer is not much of a clue as to what you have done.
     
  6. Oct 2, 2009 #5
    electric field strength is on the image - 20 N/C

    the issue here is, they want it in i, j k format
     
  7. Oct 2, 2009 #6

    Delphi51

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    Okay.
    1.6 x 10^-4 * cos(60) i + 1.6 x 10^-4 * sin(60) j + 0k
     
  8. Oct 2, 2009 #7
    thanks delphi. can you explain the cos and sin portion a bit? i never really could understand why those are used to express a single side of a triangle
     
  9. Oct 2, 2009 #8

    Delphi51

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    triangle.jpg
    Expressing a vector as a horizontal part plus a vertical part makes it very convenient to add vectors (just add the h and v parts separately without worrying about angles). Also, in something like a trajectory problem the motion in two perpendicular directions is independent, so you can do the horizontal part of the problem without worrying about the vertical part.
     
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