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Homework Help: Circular motion object falling in the circle

  1. Feb 27, 2017 #1
    1. The problem statement, all variables and given/known data
    An object with mass of m travelling in a circle rail ,when reached point A the object derailed and moved in a parabola path to point B and so on find the length of AB in term of R and theta. given that B is on the same horizontal level as A

    2. Relevant equations

    3. The attempt at a solution
    i dont get the idea .if its stop moving in circular that mean there must be no centipetal force which mean the velocity must be 0 or there must be another force with the same quantity as centipetal force.(the picture is upside down btw sorry!)

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  2. jcsd
  3. Feb 27, 2017 #2


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    The object is moving in a parabolic trajectory as shown in your figure. There is a radius of curvature to the trajectory which means that there is a centripetal force directed towards the center of the (instantaneous) circle that the object describes. This centripetal force is supplied by the appropriate component of gravity.
  4. Feb 27, 2017 #3
    Great answer Kuruman, that homework question takes me back!
  5. Mar 2, 2017 #4


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    No that's not correct.

    The magnitude of the centripetal force required to move in a circle of radius r is given by mv^2/r. If the net centripetal force is greater than that value the object will move in a tighter circle (eg smaller r).
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