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Use this form of radius vector

  1. Sep 1, 2004 #1
    Please help me! I'm not sure if this is a wright place to ask, but...

    (vector) F = r^4 r(vector)
    Find me rotor of F

    Rotor of vector F must be 0, but I don't know how :confused: . You can't use this form of radius vector: xi+yj+zk (i, j, k are vectors), just leave r.
    Thank you!!!
     
    Last edited: Sep 1, 2004
  2. jcsd
  3. Sep 1, 2004 #2

    Tide

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  4. Sep 2, 2004 #3
    Thank you..but I didn't find the wright answer there
     
  5. Sep 2, 2004 #4
    What do you need by this question ?
    let be must claire
     
  6. Sep 2, 2004 #5
    This is what I need:
    nabla x F
    F = r^4 r (bold are vectors)..(r is radius vector)
    The result of this is 0, but I don't know how...
    Thank you for your help!
     
  7. Sep 2, 2004 #6

    Tide

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    Well, if you can't or won't work with spherical coordinates then do it by brute force using the definition of curl. Just remember that the unit vector [itex]\hat r[/itex] is not a constant with respect to position!
     
  8. Sep 3, 2004 #7
    Tide, I really don't know what to do with spherical coordinates. Maybe you can show me.
    But, I found another way..Here it is:

    nabla x r^4r =
    = r^4rotr - r x grad r^4
    = 0 - r x dr^4/dr r/r
    = - r x dr^4/dr r/r
    = - dr^4/dr 1/r rxr
    = 0


    btw. bold are vectors; curl=rot; nablaxnablaf=0; rot r=0; rxr=0

    Can somebody tell me is this correct???
     
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