perpetual motion

American  

noun

Mechanics.

1. the motion of a theoretical mechanism that, without any losses due to friction or other forms of dissipation of energy, would continue to operate indefinitely at the same rate without any external energy being applied to it.

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perpetual motion British  

noun

1. Also called: perpetual motion of the first kind.  motion of a hypothetical mechanism that continues indefinitely without any external source of energy. It is impossible in practice because of friction

2. Also called: perpetual motion of the second kind.  motion of a hypothetical mechanism that derives its energy from a source at a lower temperature. It is impossible in practice because of the second law of thermodynamics

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Etymology

Origin of perpetual motion

First recorded in 1585–95

Example Sentences

"Perpetual motion" machines are the patent examiner's biggest annoyance.

From Time Magazine Archive

Perpetual motion, or squaring the circle, would baffle Gregory.

From The Face and the Mask by Barr, Robert

Now take my first, reverse its spell, 'Twill make my fourth; and he, note well, Could solve the problems mighty— To square the circle, change to gold, Perpetual motion to unfold, And make elixir vitæ.

From Harper's Young People, June 22, 1880 An Illustrated Weekly by Various

Perpetual motion has bin very nearly discovered ever since men began to try their hands at engineerin’, but it ain’t discovered yet, nor never will be—’cause why? it ain’t possible.”

From The Lifeboat by Ballantyne, R. M. (Robert Michael)

If you had willingly the belle resign'd, I was, my friend, to take a turn inclin'd; That had sufficed for me, since I, like you, Perpetual motion never can pursue.

From Tales and Novels of J. de La Fontaine — Complete by La Fontaine, Jean de