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Homework Help: Stress and Strain, simple question! Just need a clarification

  1. Jun 11, 2009 #1
    1. The problem statement, all variables and given/known data

    A tow truck is pulling a car out of a ditch by means of a steel cable that is 9.1 m long?
    and has a radius of 0.50 cm .when the car just begins to ,move , the tension in the cable is 980 N. how much has the cable stretched?

    Y steel= 2.0 x 10¹¹ N m²

    2. Relevant equations

    F/A = Y (delta L / L0 )

    3. The attempt at a solution

    We just need to solve for delta L, but I am having difficulty figuring out what A would be - any help? What A formula for the cable do I use?
  2. jcsd
  3. Jun 11, 2009 #2
    nvermind I think I got it!

    890/(2pi*r(in meters) = Y (delta L/9.1)

    is this correct?
  4. Jun 11, 2009 #3


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    Homework Helper

    the A in the equation is area, the steel is circular to [itex]A=\pi r^2[/itex] and convert r to metres.
  5. Jun 11, 2009 #4
    thanks so much!!
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