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Equations on motion for spring

  1. May 8, 2012 #1
    1. The problem statement, all variables and given/known data

    hi,
    the question asks for me to find the normal mode of the oscillator shown below
    where k1=3nm-1 k2=7.5 k3=39nm-1

    im having difficulty setting it up with gravity being the main problem

    diagram below
    nF0co.png

    2. Relevant equations


    3. The attempt at a solution


    equation of motion

    where m1 is the 2kg mass and m2 the 6kg mass

    m1[itex]\ddot{y1}[/itex]=m1g-k1y1 + k2(y1-y2)

    m2[itex]\ddot{y2}[/itex]=m2g-(k2+k3)y2

    i think my equations of motion are wrong, hence why im not able to get the right matrices, im not exactly sure what though, im missing something elementary

    thanks for your help
     
    Last edited: May 8, 2012
  2. jcsd
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