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Homework Help: Force done by the spring if a weight is attached

  1. Oct 13, 2011 #1
    1. The problem statement, all variables and given/known data

    What is the force done by the spring if an object of mass m is attached.

    2. Relevant equations

    3. The attempt at a solution

    Sum F = 0

    Therefore the force done by the spring is mg? is the +/- right? for direction? Is the force right?
  2. jcsd
  3. Oct 13, 2011 #2
    Properly think about it:

    The mass is hanging from the spring. I assume that when it is observed, it can be considered at rest.
    If it's at rest, there are only two forces acting on the mass: gravity and the spring force. Since the mass is at rest, all forces must cancel eachother.
    Since both forces are acting in opposite directions, they shouldn't have the same sign.

    You stated that Sum F = 0. Therefore, Fs + Fg = 0
  4. Oct 13, 2011 #3
    Ok so then Fs=-Fg=-mg.
    Just change the sign of my answer?
  5. Oct 13, 2011 #4
  6. Oct 13, 2011 #5
    ok thank you very much!! i thought the sign was a bit messed up.
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