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Homework Help: Meterstick against wall

  1. Oct 10, 2008 #1
    1. The problem statement, all variables and given/known data
    A 0.13 kg meter stick is held perpendicular to a wall by a 2.7 m string going from the wall to the far end of the stick.
    (a) Find the tension in the string.
    (b) If a shorter string is used, will its tension be greater than, less than, or the same as that found in part (a)?
    (c) Find the tension in a 2.0 m string.


    2. Relevant equations

    Torque=Nr?

    3. The attempt at a solution
    I discovered the angle to be 68.38 degrees, and I thought that, since the y-component of the force cancels out mg, T=mg/sin(theta). Why is it wrong?
     
  2. jcsd
  3. Oct 10, 2008 #2

    Doc Al

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    Staff: Mentor

    The string tension is not the only force (besides the weight) acting on the stick.
     
  4. Oct 10, 2008 #3
    I know that the wall exerts a horizontal force, but that doesn't matter in the Fy equation.
     
  5. Oct 10, 2008 #4

    Doc Al

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    Staff: Mentor

    But the vertical force it exerts does.
     
  6. Oct 10, 2008 #5
    wait... how does it exert a vertical force? Is there a friction force?
     
  7. Oct 10, 2008 #6

    Doc Al

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    Staff: Mentor

    There better be. But you need not worry about the wall force to solve this problem.
     
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