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Homework Help: Spring Problem Help

  1. Oct 31, 2012 #1
    1. The problem statement, all variables and given/known data

    A massless spring of length 0.270 m is in its relaxed position (left diagram). It is compressed to 71.0 percent of its relaxed length, and a mass M = 0.140 kg is placed on top and released from rest (shown on the right). The mass then travels vertically, taking 1.20 s to reach the top of its trajectory. Calculate the spring constant
    Diagram http://www.learning.physics.dal.ca/dalphysicslib/Graphics/Gtype13/prob24_CompSpring.gif

    2. Relevant equations

    3. The attempt at a solution

    I tried using conservation of energy, but kept getting stuck not being able to find how high it goes or the velocity when it leaves the spring
  2. jcsd
  3. Oct 31, 2012 #2


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    Welcome to PF!

    Hi CAPA! Welcome to PF! :smile:
    It will leave the spring when the deceleration of the end of the spring is … ? :wink:
  4. Oct 31, 2012 #3
    Re: Welcome to PF!

    we haven't really done any decelerating questions with springs. How would I go about finding that? would it be equal to gravity?
  5. Nov 1, 2012 #4


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    Hi CAPA! :smile:

    (just got up :zzz:)

    Use Fnet = ma to find the acceleration at a general displacement x.

    The mass will leave the spring when that acceleration becomes less than -g. :wink:
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