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Homework Help: Quick question on energy conversions

  1. Nov 26, 2009 #1
    A ball bearing is dropped from rest and falls at speed v just before hitting a spring. The spring compresses by a distance of y, and all energy is converted into elastic potential energy in the spring. We are supposed to find F exerted by spring.

    The conversion of energy, according to me, is
    0.5mv2 [KE]-->mgy [GPE] +0.5 Fy [EPE, imagine the Force against Displacement graph and EPE is area under it]

    However, the answer given is,
    0.5mv2-->mgy + Fy [I suppose this is work done]

    Which is correct and why? Im confused.

  2. jcsd
  3. Nov 26, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The force exerted by the spring varies as the spring compresses. Is F supposed to be the average force?
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