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Homework Help: FOrced Oscillations

  1. Oct 5, 2008 #1
    I was hoping someone could explain damping and forced oscillations. I had a couple of problems I could not do that revolved around these topics because I couldn't figure out which equations to use. Here's an example.


    1. The problem statement, all variables and given/known data
    Damping is negligible for a 0.155 kg object hanging from a light 6.30 N/m spring. A sinusoidal force with an amplitude of 1.70 N drives the system. At what frequency will the force make the object vibrate with an amplitude of 0.440 m?

    Give higher and lower frequencies.


    2. Relevant equations
    For this I used the forced oscillation equation which is basically

    Amplitude = (Fo/m)/(sqrt ((w^2 - wo^2)^2 + (damping)^2))


    3. The attempt at a solution
    So since it said damping was negligible, the damping part is 0. For wo (omega initial), I used sqrt (k/m) and plugged that in. Fo was given at 1.70N and mass was also given. I solved for omega (two different answers because it is squared) and I got 3.96Hz for the upper but it wasn't correct.





    I was hoping also someone could basically explain what equation is used for these types of problems. There is another one where mass, an equation for external force (F= 3sin(2pit)) and spring constant are given and it asks to find period, amplitude, etc. How do I incorporate the external force? I think this problem and the org problem are hand in hand so if I can figure out one, I can do the other. Any Help would be greatly appreciated!
     
  2. jcsd
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