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Forces in coupled system

  1. Oct 5, 2012 #1
    Hi

    How do you determine the forces in a coupled oscillating systems? (check the attachment for coupled oscillating system)

    I do get the forces right but I make mistakes with the signs.
     

    Attached Files:

  2. jcsd
  3. Oct 5, 2012 #2

    tiny-tim

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    welcome to pf!

    hi rsaad! welcome to pf! :smile:
    i can only suggest that you draw a very clear diagram, carefully labelling the distances, and then write out a constraint equation such as a + b + c = L :wink:

    (do you want to show us an example of your going wrong?)
     
  4. Oct 5, 2012 #3
    Thank you tinu-tim! =)
    Consider the 2nd diagram in the attachment and assume that it is attached on both ends and that x1 is extension in a and x2 is extension b.
    for mass a:

    -k (x1)
    k(x1-x2) <--- now i am not sure whether to put a negative sign with it or positive

    for mass b:
    -k (x2)
    k(x2-x1) <--- again i do not know what sign to put here.
     

    Attached Files:

  5. Oct 5, 2012 #4

    tiny-tim

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    sorry, i can't follow this :confused:

    call the points O A B C, with OC = L

    how long are OA AB and BC ?​
     
  6. Oct 5, 2012 #5
    We haven't been specific about the length in class but lets assume that L/3 = oa= ab= bc
     
  7. Oct 5, 2012 #6

    tiny-tim

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    but A and B are moving :confused:
     
  8. Oct 5, 2012 #7
    It is a screen shot at a time when the springs are stretched. I just need to understand which direction the forces apply.
     
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