1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Perpetual Motion?

  1. Jan 7, 2005 #1
    Perpetual motion has been deemed "impossible", at least in the world we live in. Why aren't the perfectly elastic collisions between gas particles considered perpetual motion?
  2. jcsd
  3. Jan 7, 2005 #2


    User Avatar

    Staff: Mentor

    There are several different characterizations of "perpetual motion" and the one you picked is physically real. There are plenty of similar examples, like a planet in orbit or a particle in motion in space.

    What is impossible are perpetual motion machines - self-powering devices that never need fuel and give off excess energy.
  4. Jan 8, 2005 #3
    Yes, you would violate the 2nd Law of Thermodynamics. Elastic collisions happen, but to control them for energy harnessing purposes...that would require inelastic processes, I suppose.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Perpetual Motion Date
I Feynman: Reversible machines, no perpetual motion? Feb 8, 2018
B Superfluid Perpetual Motion? Aug 21, 2016
Perpetual motion Oct 7, 2014
Perpetual "Motion" Jun 30, 2014
Perpetual Motion From Satellite Revolution Jan 29, 2014