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Uniform Circular Motion

  1. Oct 23, 2013 #1
    1. The problem statement, all variables and given/known data

    A ball of mass 4 kg on a string of length 1.5 m is being swung in a circle in the vertical plane at a constant speed of 10 m/s. Find the tension in the string at the bottom and top of the balls path

    2. Relevant equations

    ƩF = m(v^2/r)

    3. The attempt at a solution
    This is how I attempted to solve this problem, but my answer is not correct.
    Is it correct that the tension in the string at the bottom is: T = m(v^2/r) + mg
    And at the top: T = m(v^2/r) - mg
     
    Last edited: Oct 23, 2013
  2. jcsd
  3. Oct 23, 2013 #2

    Simon Bridge

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    Please show your working - not just some answers.

    Consider:
    T = m(v^2/r) + mg

    This is saying that, at the bottom of the path, the tension has to overcome gravity and still have enough left over to give a centripetal force.... the net force points upwards.
    Does that make sense?
     
  4. Oct 23, 2013 #3
    Yes; so the tension at the bottom would be, T = (4*(10)^2)/1.5 + 9.8*4 = 217 N. Is this correct?
     
  5. Oct 23, 2013 #4

    Simon Bridge

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    I don't check arithmetic.
    But you appear to have answered your own question.
     
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