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Tension in 2 strings

  1. Feb 20, 2008 #1
    1. The problem statement, all variables and given/known data
    Two wires are tied to the 360 g sphere shown in Figure CP7.61. The sphere revolves in a hori*zontal circle at a constant speed of 6.5 m/s. What is the tension in each of the wires?



    2. Relevant equations
    I can't figure how to find the tension. With so little given i dnt even knw where to start


    3. The attempt at a solution
     
  2. jcsd
  3. Feb 20, 2008 #2

    Dick

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    At least you've got Figure CP7.61. We don't even have that.
     
  4. Feb 21, 2008 #3
    [​IMG]
     
  5. Feb 21, 2008 #4

    Dick

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    There are three forces acting on the sphere. mg (gravity) pointing down and two different tensions pointing along the wires. Break the tensions into x and y components. The sum of their vertical components should cancel mg and the sum of the horizontal components should equal mass times the rotational acceleration of the sphere.
     
  6. Feb 21, 2008 #5
    I just figured this out minutes ago. The trick is to sum your x forces and set them equal to mv^2/r. solve that for T2. Then sum up your y forces and set them equal to 0. plug in the expression you found when you solved for T2 into the T2 of the new expression. Everything will then be in terms of T1 and you can then solve for it. Then take that answer and plug it back in for the expression where you solved for T2. You now have the tension in both of your wires.

    Hope this is somewhat helpful
     
  7. Feb 21, 2008 #6
    thanks man i think i got this one down
     
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