Is the Rotor of This Radius Vector Correct?

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Discussion Overview

The discussion revolves around the calculation of the curl (or rotor) of a vector field defined as F = r^4 r, where r is the radius vector. Participants are exploring the methods to compute the curl, particularly in the context of spherical coordinates and the implications of the vector's form.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about calculating the curl of F and suggests that it should be zero.
  • Another participant recommends using the spherical coordinate form of the curl, providing a link for reference.
  • A participant indicates that they did not find the correct answer using the suggested resource.
  • Further clarification is requested regarding the specific needs of the question.
  • One participant attempts to derive the curl using a step-by-step approach, ultimately concluding that the result is zero, but seeks confirmation of their method.
  • Another participant suggests using the brute force definition of curl if spherical coordinates are not preferred, noting that the unit vector \hat r varies with position.

Areas of Agreement / Disagreement

There is no consensus on the correct method to compute the curl or whether the result is indeed zero. Multiple approaches are suggested, and participants express differing levels of familiarity with the necessary mathematical tools.

Contextual Notes

Participants mention the importance of understanding the behavior of the unit vector \hat r in relation to position, indicating that assumptions about its constancy may not hold. There are also references to specific mathematical operations that may require further clarification.

Who May Find This Useful

This discussion may be useful for individuals interested in vector calculus, particularly those looking to understand the computation of curl in different coordinate systems and the implications of vector field definitions.

xz5x
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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:
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Thank you..but I didn't find the wright answer there
 
What do you need by this question ?
let be must claire
 
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!
 
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!
 
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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