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Homework Help: Mechanics problem of rings

  1. Apr 13, 2013 #1
    1. The problem statement, all variables and given/known data

    A ring of mass 100gm connecting freely two identical thin loops of mass 200gm each, starts sliding down from point A at t=0. The centres of loops are B and C.The loops move apart over a sufficciently rough horizontal surface.[Neglect the friction between the ring and the hoop]g=10 Find
    i) The normal reaction acting on each loop given by the horizontal surface at t=0
    ii)Acceleration of loop at t=0
    Given angle ABC=ACB=45

    2. Relevant equations

    I had no idea of it...What to use?

    3. The attempt at a solution
    I tried to balance the forces acting at point A. but get nothing ..Thanks for help.
  2. jcsd
  3. Apr 13, 2013 #2
    Is there a diagram for this problem? I am at loss trying to understand the setup.
  4. Apr 13, 2013 #3
    See i had a diagram..but it is in GGB FILE..For at loss.. I am telling Draw two intersecting circles..Name the topmost point as A..The ring is at A and the centres of the circles are B and C.B and C are the loops. Did it help?? or what's your confusion??
  5. Apr 13, 2013 #4
    Sorry, it is still unclear. Can't you take a screenshot and attach it here?
  6. Apr 13, 2013 #5
    Sorry i don't have a mobile..But what's your problem..Tell .I shall try my best to clear it.
  7. Apr 13, 2013 #6


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    Science Advisor
    Homework Helper
    Gold Member

    Seems they're rigid hoops, not loops, standing on a rough horizontal surface. The ring is arbitrarily small.
    BBAI BBAI, Can you draw free body diagrams for the ring and for one hoop? What forces are there in each case? What equations can you write down (not forgetting everything is accelerating)?
    Note that the geometry will give a relationship between the acceleration of the ring and the acceleration of the hoops.
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