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Math Help - where am i going wrong?

  1. #1
    ADY
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    where am i going wrong?

    usings youngs modulus, i need to figure out the extension in a cable...now

    m = 950kg
    youngs modulus of steel = 210 GN m^-2
    diameter = 11.5929mm

    so where am i going wrong?

    f = m x g
    f = 950mg x 210GNM^-2
    f = 1.995 x 10^14 kg m^-2
    f = 1.995 N

    stress (as i dont have a sigma symbol, ill use 's')
    s = f / a
    s = 1.995 N / 11.5929mm
    s = 0.1720

    extension = s x original length
    e = 0.1720 x 8
    e = 1.376mm

    Thanks Guys
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  2. #2
    ADY
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    if it helps, the total length of the cable is 8m
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  3. #3
    ADY
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    could someone confirm this is not right please

    and show me what i've missed? its due in tommorow
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  4. #4
    ADY
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    is this right?



    σ = Force
    Area
    σ = 9500 N
    0.105556 x 10-3 m2
    E = σ Transpose to ε =σ
    ε E
    ε = 90 x 106 N M-2
    210 x 109 N M-2
    ε = 0.000428 (No units because its an extension)
    ε = Δl Transpose to Δl = ε
    l l
    Δl = 0.000428 x 8m
    Δl = 0.003424mx 1000
    Δl = 3.42mm
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