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Sketching vector fields

  1. Mar 31, 2009 #1
    1. The problem statement, all variables and given/known data

    I am asked to sketch the following vector field in the xy-plane

    (a) F(r) = 2r


    (b) F(r) = -r/||r||3


    (c) F(x,y) = 4xi + xj

    2. Relevant equations



    3. The attempt at a solution

    Can someone please give me some hints on how to proceed
     
  2. jcsd
  3. Mar 31, 2009 #2

    lanedance

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    hi EquinoX

    first I would look at the direction and magitudes of the vectors & see if you can spot any symmetries

    a good way to start is to sketch the vector at several points as well
     
  4. Mar 31, 2009 #3
    yes but for F(r) = 2r this is a 3D vector field, so if I am asked to sketch it in an xy plane, do I just look at the i + j direction? and is 2r basically just 2xi + 2yj + 2zk?

    because r is xi + yj + zk?
     
    Last edited: Mar 31, 2009
  5. Mar 31, 2009 #4

    lanedance

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    Yeah i think that should do

    r = sqrt(x^2 + y^2 + z^2) and in the xy plane z = 0, so this shouldn't affect your r anyway
     
  6. Mar 31, 2009 #5
    so r = sqrt(x^2)i + sqrt(y^2)j ?
     
  7. Mar 31, 2009 #6

    lanedance

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    sorry bit of confusion over notation
    |r| = sqrt(x^2 + y^2 + z^2)

    r = xi + yj + zk
     
  8. Mar 31, 2009 #7
    I am asking 2r?
     
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