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Homework Help: Reaction force between a Sphere and particle

  1. Apr 16, 2009 #1
    http://img13.imageshack.us/img13/9112/70948888.th.jpg [Broken]

    I do not understand how circular motion can be occuring a point B - surely at B, the reaction force occurs in a direction away from O. Therefore, there is no resultant force that can be acting towards O, since the weight is perpendicular to OB.

    Can someone please explain this.

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Apr 16, 2009 #2
    Well I'm interested in this problem as well.
    What I thought so far:
    If we had a hoop rotating and the particle at point A-we couldn't pass point B from the exact reason You stated above.
    But this time it has initial velocity, so in point B it has velocity, so there is fictitious centrifugal force,That's what i think...
    well good luck..
    Last edited by a moderator: May 4, 2017
  4. Apr 16, 2009 #3

    Doc Al

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    Staff: Mentor

    Realize that the particle is riding on the inside of the sphere, just like a car on the inside of a rollercoaster loop. The surface is curved, not flat, thus the surface must press in on the particle (towards O) exerting a centripetal force on the particle.
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