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Homework Help: Minimum speed to maintain a circular trajectory

  1. Oct 1, 2008 #1
    1. The problem statement, all variables and given/known data
    a rock of mass 0.500 kg is tied to a string of radius 75 cm and is revolving in a vertical circle at a uniform speed. determine the minimum speed for the rock to maintain a circular trajectory without the string collapsing (not staying taut). (Hint: where would that occur in the trajectory?)

    m=0.500 kg
    r=.75 m

    2. Relevant equations


    3. The attempt at a solution

    v=(gr)^(1/2) (square root of g*r)
    v=2.7 m/s
    i don't know where i use the mass of 0.500 kg
  2. jcsd
  3. Oct 2, 2008 #2


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    Staff Emeritus
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    Gold Member

    Are you sure that the weight of the rock is the only force acting? Furthermore, are you sure that the weight of the rock always acts radially?
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