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Homework Help: Work Done by a Spring Force and block problem

  1. Apr 6, 2009 #1
    1. The problem statement, all variables and given/known data


    gives spring force Fx versus position x for the spring–block arrangement


    The scale is set by Fs = 160 N. We release the block at x = 16.0 cm. How much work does the spring do on the block when the block moves from xi =+8.0 cm to x=+7.0 cm

    2. Relevant equations

    Fs = -kd

    W = Fd

    3. The attempt at a solution

    Fs/d = k

    160N/0.16m = k

    1000 = k

    kd = F

    1000*1m = 1000N

    1000N * 1m = W

    W = 1000J

    I don't know how to this question please help.
  2. jcsd
  3. Apr 6, 2009 #2


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    When it is stretched to 8 cm how much PE is in the spring?

    As it moves back to 7 cm how much potential energy is in the spring?

    Isn't the difference then the Work that went to kinetic energy?
  4. Apr 6, 2009 #3
    I disagree with your equations. Force isn't constant, so I don't think you can use W = Fd

    Edit: Actually, I may be wrong... I didn't notice that graph you posted up top. I've never seen a spring problem set up with a graph like that before. Disregard this post. :-p
  5. Apr 8, 2009 #4
    PE is just PE = 1/2kx^2

    but how do we find k?

    160N/0.16m = k

  6. Apr 8, 2009 #5


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    That's what I would use.

    F = kx so ... why not? The graph says it's linear.
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