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Homework Help: Simple harmonic motion - Springs

  1. Jun 18, 2012 #1
    1. The problem statement, all variables and given/known data

    I have trouble determining the system of forces in systems with strings like the following:

    2. Relevant equations

    3. The attempt at a solution

    My guess is it is:

    x1=L/3 x2=2L/3

    mass 1: -kx1+k(x2-x1)=m1a1
    mass 2: -k(x2-x1)+kx1=m2a2

    I'm not sure it is correct. Even if it is, anyone knows a good way to see the correct signs of the forces? I have some trouble identifying them...

    Thanks ahead!
  2. jcsd
  3. Jun 19, 2012 #2
    Hi Jalo! :smile:

    I believe the question lacks information. Your title says springs and the question states strings. :tongue2:

    Alsos, there is nothing mentioned about the elastic constant 'k', nor about which forces do you require. If all the forces, it would have to include gravitational force too....
  4. Jun 19, 2012 #3
    The criterion for SHM is that the restoring force be proportional to the displacement from the equilibrium postiion.
    You have to the equilibrium configuration.
    Last edited: Jun 19, 2012
  5. Jun 19, 2012 #4
    Constank k, no gravitational force, and just imagine it as springs. hope that helps :P
  6. Jun 19, 2012 #5
    What is their natural length? By how much are they compressed/extended from mean position??
  7. Jun 19, 2012 #6
    The problem doesn't give any data other the one I wrote.
    However I managed to solve the problem. Thanks to all who tried to help. :)

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