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Homework Help: Spring and Mass

  1. Nov 23, 2014 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    Fs = -kx

    w = mg

    3. The attempt at a solution

    I said that when the spring is stretched out at its max, the weight pulling down will equal the force of the spring pulling up.

    -kx = mg
    -(1500)(x) = (3)(-9.81)

    x = 0.01962 m

    The solution key tells me the max stretch is double this amount, 0.039 m. What is wrong with my approach?
  2. jcsd
  3. Nov 23, 2014 #2


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    Science Advisor
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    2017 Award

    Mark the word suddenly. If the basket were at maximum distance and forces would be in equilibrium, the velocity wouldn't change anymore, so the thing would hang still.
    Do you think that is what would happen if you suddenly put a brick in the basket ?
    Last edited: Nov 23, 2014
  4. Nov 23, 2014 #3
    Ah. I see. So then I need to solve the problem using the conservation of energy.
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