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Homework Help: Energy conversions of a moving spring

  1. Oct 25, 2009 #1
    1. The problem statement, all variables and given/known data
    The energy change of a oscillating spring. It involves SHM and the energy involved are GPE, KE and Elastic PE (EPE).

    3. The attempt at a solution

    I understand the other conversions e.g. On the downward journey above the equilibrium position, the gravitational p.e. is changed to elastic p.e. and k.e.

    But there is one part I dont understand:
    On the upward journey above the equilibrium position, the k.e. and elastic p.e. are changed to gravitational p.e.

    Shouldnt there be elastic PE when it is compressed as in 'compressed energy'? ( k.e. changed to EPE and GPE) or is there a gross misunderstanding on my part? In hooke's law, the 'x' means extension but does it count compression distance?

  2. jcsd
  3. Oct 25, 2009 #2


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    To elongate and compress a spring from its equilibrium position, external work has to be done. This work is stored in the form of GPE and EPE.
  4. Oct 26, 2009 #3
    But at the peak, the answer says there is ONLY GPE. But I though there is 'compression' energy or EPE there too?
  5. Oct 26, 2009 #4


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    To start the oscillation, you have to do work on the spring, either by compressing or pulling it down. When it starts it oscillates due to gravitational force only. Hence at the peak All KE is converted to GPE.
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