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Homework Help: Forced oscillation (mass & spring)

  1. Nov 2, 2008 #1
    1. The problem statement, all variables and given/known data
    A 2 kg object attached to a spring moves without friction and is driven by an external force given by F = (3.00N)sin(2[tex]\pi[/tex]t). The force constant of the spring is 20.0N/m.
    Find the amplitude of the motion.


    2. Relevant equations
    I am not sure but I am trying to use:
    A = (F0/m)/[tex]\sqrt{}(w^2-w0^2)^2[/tex]


    3. The attempt at a solution
    Applying this equation using w equals 2pi and w0 is k/m (10) gives an amplitude of 0.00173. The solution in the book says 5.09cm.
    Am I approaching this question correctly?
     
  2. jcsd
  3. Nov 2, 2008 #2

    alphysicist

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    Homework Helper

    Hi kash25,
    w0 is not equal to k/m. If you correct this you should get the right answer.
     
  4. Nov 2, 2008 #3
    Not exactly sure...but that equation you have might be for forced oscillations working against friction; in this case there is no friction.
     
  5. Nov 2, 2008 #4

    alphysicist

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    No, it's the right equation. If it was a damped spring there would be another term under the radical. Using that equation (with the corrected value for w0) gives the answer given in the post.
     
  6. Nov 2, 2008 #5
    remember that w0 = sqrt (k/m).

    That will give you the right answer :)
     
  7. Nov 2, 2008 #6
    stupid mistake..thanks for your help!
     
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