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Homework Help: Centripetal Force with angle problem

  1. Oct 26, 2011 #1
    1. The problem statement, all variables and given/known data
    Consider the figure below, a ball of mass m=0.100 kg tied by a string of 0.100 m travels in a circular motion with 2 revolutions per second. Find the angle θ that keeps the ball stationary.
    Given: m = 0.100 kg, v = 2 rev/sec L = 0.100 m (radius?)
    [PLAIN]http://img192.imageshack.us/img192/9518/unledrht.jpg [Broken]

    2. Relevant equations
    FC = [itex]\frac{mv^{2}}{r}[/itex]

    3. The attempt at a solution
    Let T be the tension force.
    y: Tcosθ - mg = 0
    x: Tsinθ = mv2/r

    The problem is I am not sure if the setup above is right, and should I take the length of the string as the radius? or rsinθ?
    Hope you guys can help me, thank you very much, I will be extremely appreciated!!
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 27, 2011 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    I don't understand the question. If the ball is moving it is not stationary. Is this a pendulum? Is it horizontal or vertical? Please give us the exact wording of the question.

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