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Homework Help: Work done by stretching a STring

  1. Apr 11, 2008 #1
    I have been looking all over for an equation to find the work done on a steel string that is stretched L meters.

    "Find the work needed to stretch the string."

    I know it has variable forces so I was thinking I could use elastic potential

    [tex]U=\frac{kx^{2}}_{2}[/tex]

    but now I have the problem finding out what K is.

    ANY help is appreciated thanks.

    Nick
     
  2. jcsd
  3. Apr 11, 2008 #2

    Dick

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    Is this a homework problem? That can't be the full question. You've got the right idea if the steel wire can be considered as a spring. You'll need a modulus of elasticity and the geometry of the wire to actually do this.
     
  4. Apr 11, 2008 #3
    yea I have the area of the wire and the modulus... I just need help figuring out which equation to use.

    Thanks,
    Nick
     
  5. Apr 11, 2008 #4

    Dick

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    Didn't they give you a formula for that as well? The elastic modulus Y, has units of N/m^2, yes? k should have units of N/m. So I would guess on purely dimensional grounds that if L is length and A is cross sectional area that k=Y*A/L. Can you confirm that by doing some research? Units are your friend. Exploit them.
     
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