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Young's Modulus of wire

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data
    "A brass wire with Young's modulus of 9.1 1010 Pa is 2.1 m long and has a cross-sectional area of 4.6 mm2. If a weight of 5.0 kN is hung from the wire, by how much does it stretch?"

    The answer is to be given in cm.

    2. Relevant equations

    I used the equation for Young's Modulus, YM = (F/A) / ([tex]\Delta[/tex]L/L0)

    3. The attempt at a solution

    I looked at my given info first.
    YM = 9.1e10
    Area = 4.6 mm2 = 0.46 cm2
    Force = 5 kN = 5000 N
    L0 = 2.1 m = 2100 cm

    I converted all my units to cm because that's what the answer should be in.

    Then I plugged that info into my Young's Modulus equation:

    9.1e10 = [(5000)/(0.46)] / [([tex]\Delta[/tex]L)/2100)]
    [tex]\Delta[/tex]L = (5000)(2100) / (.46)(9.1e10)
    [tex]\Delta[/tex]L = 2.5e-4

    I thought I set this up right, but maybe I'm missing something.
  2. jcsd
  3. Dec 8, 2008 #2


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    Homework Helper

    I'd keep everything in meters.

    Then convert for the answer.
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