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Homework Help: Need to find the spring constant

  1. Dec 12, 2009 #1
    1. The problem statement, all variables and given/known data
    A series of masses are hung from a vertical spring and the length is measured in each case to the nearest milimeter. Data below:

    Mass : Spring Length
    050g : 40.2cm
    100g : 45.8cm
    150g : 50.9cm
    200g : 56.4cm
    250g : 61.4cm
    300g : 66.9cm
    350g : 73.7cm
    400g : 81.2cm

    I need to find the spring constant.

    2. Relevant equations

    Fs = k | l - l0| ,
    Fs = Spring Force
    k = spring constant
    l = length of spring
    l0 = initial length of spring

    3. The attempt at a solution
    I know that Fs = Fg = mass / 100 (using g = 10 N/kg).
    I just don't know how to get the constant because I don't know what the initial spring length is (it's not 0).
  2. jcsd
  3. Dec 12, 2009 #2


    User Avatar

    Think about the equation F = kX for a moment. What kind of graph does that make? What one of those letters represents the slope of that graph?

    Can you put those hints together to figure out a way to determine the spring constant?
  4. Dec 12, 2009 #3
    Oh, okay. It's the same for any initial length. Thanks :)
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