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Homework Help: Spring in a motionless elevator

  1. Sep 26, 2011 #1
    1. The problem statement, all variables and given/known data

    A single mass m1 = 3.1 kg hangs from a spring in a motionless elevator. The spring is extended x = 11 cm from its unstretched length.
    1)What is the spring constant of the spring?

    2. Relevant equations


    3. The attempt at a solution

    Having trouble setting this one up. I know it is easy but the spring confuses me. I drew a free body diagram and I am still lost.
  2. jcsd
  3. Sep 26, 2011 #2
    Hi there! The only forces on the mass will be the weight force (w = mg) pulling down, and the spring force (F = -kx) pulling up. Since the mass is not accelerating, these two forces will be equal and opposite.
  4. Sep 26, 2011 #3
    Yup, got it. -kx=mg. Durrrr. Thanks.
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