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Homework Help: Straightening the string

  1. Jan 25, 2009 #1
    1. The problem statement, all variables and given/known data

    http://img134.imageshack.us/img134/781/86393071cs1.jpg [Broken]
    The figure shows a string with its ends attached to a wall. What weight should be hung at point p so that the lower part of this string becomes completely horizontal?

    3. The attempt at a solution
    I dont think the string can be horizontal.
    I drew the FBD for point p.
    since tension is same throughout.
    the horizontal part of the string applies t [tex]\hat{i}[/tex]
    the weight applies -w [tex]\hat{j}[/tex]
    the upper part of the string applies -t sin x [tex]\hat{i}[/tex] +t cos x [tex]\hat{j}[/tex]

    where x is the angle made by the upper part of the string with the vertical.
    Point p cannot be in equilibrium whatever the magnitude of w be.
    Am I right?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 25, 2009 #2


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    Science Advisor
    Homework Helper

    ritwik06: No, point P is in static equilibrium, unless it is accelerating. Were properties for the string given? Tension is not the same throughout the string if a tangential force component is applied in the middle of the string, by an object that is not allowed to slip or roll, right? If the string elongates greatly under the applied load, couldn't the lower segment of the string become horizontal? Try it again.
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