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Resonant frequency of this pendulum?

  1. Sep 16, 2013 #1
    Hi everyone,

    I'm planning a simple experiment for my school, which involves fixing a mass M onto a rod of length L made of a copper alloy.

    Suppose I drive it capacitively, how do I find the resonant frequency of this simple oscillator? I need its resonant frequency to be about 400-500Hz, which would depend on it's geometry.

    I know its:

    -modulus of elasticity
    -Shear modulus
    -torsion constant


    I have found that the force varies on sin2(ωt), so the drive frequency of the oscillator is the drive frequency of the voltage. I know that at resonance, the amplitude is approxiamtely

    ≈ Q(τ/k)

    but what I need to find is its resonant frequency.
    Last edited: Sep 16, 2013
  2. jcsd
  3. Sep 16, 2013 #2


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    There is a formula for the required force to bend a beam with a certain height (here: width) and length by a certain amount. That will look like a spring constant, so you can solve it similar to a spring pendulum.
  4. Sep 17, 2013 #3
    I see, do you know where I can look up an explanation of the formula?
  5. Sep 17, 2013 #4


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