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Effecieny of a pedulum

  1. Sep 30, 2009 #1
    My project is to build an efficient pendulum that hold 75% of its amplitudeafter 1 minute. What are some things that affects how efficient its amplitude?
    Last edited: Oct 1, 2009
  2. jcsd
  3. Oct 1, 2009 #2
    anyone help?
  4. Oct 1, 2009 #3
    I think a high density pendulum bob is important, because it will reduce the air drag damping per unit mass. Note that the mass scales as the 3/2 power of the cross sectional (drag) area, so high mass also helps. A long string will reduce the pendulum frequency, which will also reduce the damping. Note that pendula in clocks are pancake-shaped for a reason (to reduce air drag). An interesting experiment is to have two nearly identical pendula mounted on the same frame. If only one is initially swinging, eventually most of the energy will transfer to the second one (coupled oscillator).
    A friend of mine built a grandfather clock, and when it was assembled, started it up in his living room, on a soft hi-pile rug. He was puzzled when the winding weight chain started swinging in unison (or in phase quadrature) with the pendulum.
    Bob S
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