Robert Boyle in 1660 conducted experiments where he pumped air out of a vessel with a swinging pendulum. He discovered that the damping rate of the pendulum is independent of the number density of the particles. At what pressure this stops being true?

  • $\begingroup$ When the means free path of particles becomes comparable to the size of the pendulum body. Certainly when the mean free path becomes comparable to the diameter of the vessel. $\endgroup$ Oct 15, 2021 at 20:02
  • $\begingroup$ I assume after that since collisions are very infrequent that the damping actually does not exist? $\endgroup$
    – emir sezik
    Oct 19, 2021 at 9:52


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