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SHM, Resonance, Pendulums

  1. Feb 29, 2004 #1
    You have 2 pendulums attached to the same peice of horizontal string.
    One pendulum has a large mass, the other is small.
    They are both of the same length.
    The large pendulum is released from an amplitude and so the small pendulum resonates.
    The rate of exponential decay of the large pendulum is much slower, than if it were a single pendulum connected to nothing else.
    How and Why is this so?
    Surely the rate of exponential decay of the large pendulum should be faster and the pendulum dampened, as when energy is transferred to the small mass pendulum, some is lost from the system as it is converted to heat?

  2. jcsd
  3. Feb 29, 2004 #2


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    From whence does this info come? Did you do an experiment?
  4. Mar 2, 2004 #3
    This is very interesting. Allow me to venture clarification of the setup: A 1 foot string is tacked to the end of my desk. At the end of that string I place a 1 ounce weight. At the middle of the string I place a 1/2 ounce weight.
    I hold onto the 1 ounce weight and taughtly raise the string structure horizontally to the edge of my desk.
    Then I let go and observe the motion of the weights as they swing down and pendulum.
    Is this a fair description?
  5. Mar 4, 2004 #4
    Yes they're experiment results, which had me puzzled for a while!
    But then i figured.....FRICTION!!
    the pendulums which were in resonance had less friction than the single pendulum on its own, therefore the systematic error was reduced and the rate exponential decay was less.
    Thanks for the replys though!
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