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Homework Help: Concept Question: Work done by a Spring

  1. Dec 6, 2009 #1
    I just need confirmation that I'm thinking of this in the right way. It's looks so simple that I feel I'm overthinking things and messing up.

    You are holding onto a spring that is already stretched. You then proceed to take that spring to equilibrium slowly.

    (a) The work you do is positive.
    (b) The change in potential energy of the spring is positive.
    (c) Your work is double that of the work of the spring.
    (d) The spring does negative work.
    (e) The spring does positive work.

    Es = 1/2 * K * x^2, where x is the amount compressed. Since it's outstretched, that'd mean x is negative, right?
    In that case, you'd start with negative energy and moving to zero. The spring is resisting the stretch and trying to pull back, which is the same direction as the spring's distance is going. So that would mean the spring's doing positive work.

    Would e) be the correct answer or is my understanding wrong?
  2. jcsd
  3. Dec 6, 2009 #2
    If the displacement is in the same direction as the force, the work is positive.
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