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Amount a string stetches out

  1. Oct 24, 2011 #1

    hm8

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    1. The problem statement, all variables and given/known data
    A 12 inch long string with a 0.5 mm diameter and is composed of a 10GPa modulus
    material is fixed at one end and loaded by a 100 g mass at its other end. What is the length
    of the string when it is under load? (Note that the length is necessarily greater than 12
    inches.)

    LInitial = 12 in = .305 m
    A = ∏r2 = ∏(.00025)2 = 1.96 * 10-7 m^2
    E = 10 N/m2
    F= .1 * 9.8 = .98 N


    2. Relevant equations

    F=kx

    k=(EA)/L


    3. The attempt at a solution

    Basically I'm just not sure which length to use for finding the spring constant k, the final or initial length?

    So should be solving something like this for final length?

    F=(EA/Lfinal)(Lfinal-LInitial)

    or this:

    F=(EA/Linitial)(Lfinal-LInitial)
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 25, 2011 #2

    PhanthomJay

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    Science Advisor
    Homework Helper
    Gold Member

    Use this one. But first correct your value for E you are way off in the number of zeroes after the '10'.
     
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