AAPT Abstract Archive

Abstract Information

  Session: Upper Division and Graduate
  Paper Type: Poster
  Title: Damped Oscillations of a Free Piston in a Gas-Filled Cylinder
  Meeting: 2017 Summer Meeting: Cincinnati, Ohio
  Location: N/A
  Time: 8:30PM
  Author: Carl E. Mungan,, United States Naval Academy,
410-293-6680, mungan@usna.edu
  Co-Author(s): None
  Abstract: If a cylinder is capped off by a sliding piston, we have a situation analogous to a mass on a spring. With suitable idealizations (hanging vertically in vacuum from a Hookean spring attached to a rigid support), the mass on the spring is undamped and it will oscillate forever if initially displaced from equilibrium. With other suitable idealizations (the piston has no friction with the cylinder, the gas is ideal with no viscosity or turbulence, there is vacuum on the other side of the piston, the piston and cylinder have zero thermal conductivity and heat capacity) will the piston similarly oscillate forever if initially displaced? No! Unlike the solid bonds inside a spring, the gas molecules are mobile and so the analog is not exact. In fact, the motion of a piston in a gas-filled cylinder is always damped [1]. However, the damping is weak and so the frequency of oscillation in a Ruchardt experiment closely approximates the undamped frequency.
  Footnotes: [1] C.E. Mungan, "Damped oscillations of a frictionless piston in an adiabatic cylinder enclosing an ideal gas," European Journal of Physics, Vol. 38 (2017).
  Presentation: Mungan_PST1C09.pdf

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