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Homework Help: Rotation and curl? (Vector calc)

  1. Apr 4, 2012 #1
    1. The problem statement, all variables and given/known data
    Give an example of a rigid body that has:
    Rotation but not curl
    Curl but not rotation
    Rotation and curl
    Neither rotation nor curl

    3. The attempt at a solution
    i don't even get what rotation is. Or curl, to be honest...*sigh* Maybe if you help me I can begin to understand. My book is making me want to bash myself over the head, it's so unhelpful x(
  2. jcsd
  3. Apr 4, 2012 #2


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    Science Advisor

    Curl only applies to vector fields. The only vector field associated with a rigid body that you can take a curl of is the velocity field. Curl of a velocity field of a rigid body is simply proportional to the angular velocity of said body. So a rigid body is either rotating and has curl of velocity field, or it is not rotating and has zero curl of velocity field. With fluids you can get more creative, but with rigid bodies, these are your options. So I'm not sure the question makes sense. It's almost like answer to one of the questions, rotating rigid body, was accidentally put into the question, making the rest of it nonsensical.

    Or I could be missing something. But it doesn't make any sense to me.
  4. Apr 4, 2012 #3
    It says for a rigid body or fluid in motion...
    I think she wants real world examples... I agree that it is confusing
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