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[Mechanics] Circular motion outside sphere

  1. Apr 24, 2016 #1
    1. The problem statement, all variables and given/known data
    A marble rolls from the top of a big sphere. What is the angle θ when the marble is about to leave the sphere? Assume a zero speed at the top.

    2. Relevant equations
    The question came from the chapter Mechanics - circular motion.

    3. The attempt at a solution
    I can't conceive what that instant moment means to the acceleration or velocity of the marble.
  2. jcsd
  3. Apr 24, 2016 #2


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    I don't really understand your question. Do you have any ideas how to solve this problem?
  4. Apr 25, 2016 #3
    Assumption:A light push is given to the marble.it starts to fall with 0 velocity.
    The moment when the ball 'leaves the sphere' is when the normal force between them is 0. Apply conservation of energy and make an expression for centripetal force at the instant when the normal force exterted by the marble is 0.
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