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Rotational speed at axis of rotation?

  1. Sep 8, 2013 #1
    Hello everyone!

    This is probably the stupidest question that I've come up with, and I'm a little embarrassed asking it, but here goes:

    Is it only the tangential speed that is zero of a point at the axis of rotation in a rotating solid? If not, then I don't understand how the rotational speed of a point in a rotating solid exactly at the axis of rotation could be zero unless it is somehow detached from the rest of the whole solid. I mean solids behave all-in-one-piece right? So it has to be rotating with the rest of it? :confused:
  2. jcsd
  3. Sep 8, 2013 #2


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    There is the tricky problem of how small the point is or how close you can get to the centre. For example if the point you refer to is much much smaller than an atom issues such as "solids behave all-in-one-piece right" become irrelevant. At the same time if it's not zero size then it behaves like any other size point.

    Consider how these two change as you approach the centre..

    The angular velocity (degrees or radians/second)
    The tangential speed
  4. Sep 8, 2013 #3
    That made me chuckle. :biggrin:

    The tangential speed changes, but the angular velocity is the same for all points, I think. (except for the one smaller than an atom, as you mentioned)

    Thank you very much for your help. I appreciate it. :smile:
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