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Homework Help: Work-Energy Problem

  1. Apr 19, 2012 #1

    Is this answer wrong? I think they've made a mistake in the work done by the spring, which I think should be (1/2)(135)(0.5)^3?
  2. jcsd
  3. Apr 19, 2012 #2
    No, the potential energy of a spring is indeed [itex]U = \frac{1}{2} k x^2[/itex]. If you want to think of it as work, then know that the spring force is [itex]F = k x[/itex], so the work done is
    [tex] W = \int F dx = \int k x dx= \frac{1}{2} k x^2,[/tex]
    which is the same answer.
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