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Homework Help: Spring constant question

  1. Jun 21, 2005 #1
    I just have no idea how to approach this simple problem.
    When a 300g mass is hung from the end of a vertical spring, the spring's length is 40 cm. With 500g hanging from it, its length is 50cm. What is the spring constant of the spring (N/m)?
    Last edited: Jun 21, 2005
  2. jcsd
  3. Jun 21, 2005 #2


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    How much did the length of the spring change?
    How much did the mass change?

    What are the units of the spring constant?
  4. Jun 21, 2005 #3
    Hooke's Law relating spring force F to spring constant k, resting length x0, and stretched length x:

    [tex] F \, = \, -k\{x - x_0\} [/tex]

    2 equations in 2 unknowns:

    [tex] \mbox{ (0.300 kg)(9.8 m/sec^2) } \ = \ -k \left \{ \mbox{ (0.40 m) } \, - \, x_0 \right \} [/tex]

    [tex] \mbox{ (0.500 kg)(9.8 m/sec^2) } \ = \ -k \left \{ \mbox{ (0.50 m) } \, - \, x_0 \right \} [/tex]

    solve for k.
    Last edited: Jun 21, 2005
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