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Homework Help: Green's Theorem not working in this problem HELP

  1. Jul 21, 2008 #1
    I have a problem from line integrals.
    My question is attached as a jpeg.
    Green's theorem is not valid for mine and i couldnot find a way.
    Pls take care of it.
     

    Attached Files:

  2. jcsd
  3. Jul 21, 2008 #2
    Should you show your attempt?
     
  4. Jul 21, 2008 #3

    Defennder

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    What does the last sentence mean?
     
  5. Jul 22, 2008 #4
    It is just a clue. It goes on with saying this kind of functions can be created without much effort and asks how they are written.
    And unfortunately i don't have much idea how to approach the problem.
     
  6. Jul 22, 2008 #5

    Defennder

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    I would say that the hint given is a big one indeed. It would save you a lot of computational effort if you understood it correctly. Have you learnt about potential functions and conservative vector fields yet?
     
  7. Jul 22, 2008 #6
    Actually, i predicted that but could not be sure. Than the answer is 0 since this is a conservative field and surface is a complete circle right?
     
  8. Jul 22, 2008 #7

    HallsofIvy

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    Since Green's theorem does not work here, then you need to directly integrate around the circle. What parameterization can you use for a circle about the origin with radius r?
     
  9. Jul 22, 2008 #8

    Defennder

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    Yep, that should be it. Although it's more correct to say it's a line integral over a closed curve.
     
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