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Rotational motion with inertial forces

  1. Sep 8, 2016 #1
    1. The problem statement, all variables and given/known data
    Capture.PNG

    2. Relevant equations

    Centripetal acceleration$$=\omega ^2R$$
    Coriolis acceleration $$=2v_{rot}\omega $$
    3. The attempt at a solution

    Think of the mass as lying on an incline. The forces I know are parallel to the incline are $$mgsin(\alpha), \mu N$$
    Forces I know are perpendicular to the incline are $$mgcos(\alpha),N$$. What I'm unsure about is how to deal with centripetal and coriolis forces. Could someone shed some light on this?
     
    Last edited by a moderator: Sep 8, 2016
  2. jcsd
  3. Sep 8, 2016 #2

    BvU

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    Hi,
    Does the block move in the rotating frame of reference ? So what about the Coriolis force ?
     
  4. Sep 8, 2016 #3
    As seen by an observer relative to whom the cylinder is rotating, the block is stationary. That must mean that it is moving in the rotating frame of reference. So there must be a Coriolis force on the block, right? I don't think there is any centripetal force on the block in the rotating frame.
     
  5. Sep 8, 2016 #4

    BvU

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    The exercise wants you t find ##\omega##s for the case the block does not slip !
     
  6. Sep 8, 2016 #5
    Yes, does not slip relative to a stationary observer who sees the cylinder as rotating. I can see that.
     
  7. Sep 8, 2016 #6

    BvU

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    More imporantly: "stays still wrt the rotating cylinder" !
     
  8. Sep 8, 2016 #7
    Oh..so it is rotating... No coriolis force in that case, just centripetal and centrifugal (in the block's frame) then?
     
  9. Sep 8, 2016 #8

    BvU

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    Yes. Some gravity and some friction too :smile:
     
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