perpetual motion

noun Mechanics.

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.

Origin of perpetual motion

First recorded in 1585–95

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for perpetual motion

Historical Examples of perpetual motion

Closely associated with his book one also finds texts dealing with perpetual-motion devices, which we shall consider later.
On the Origin of Clockwork, Perpetual Motion Devices, and the Compass
Derek J. de Solla Price
His cottage was quite a curiosity-shop of models of engines, self-acting planes, and perpetual-motion machines.
Lives of the Engineers
Samuel Smiles
This is what a perpetual-motion machine would be if such a machine were possible.
The Story of Great Inventions
Elmer Ellsworth Burns
But we give the description in the language of the inventor, as a fair type of this class of perpetual-motion machines.
The Seven Follies of Science [2nd ed.]
John Phin
Many inventors of perpetual-motion machines offer their poverty as an excuse for not making a model or working machine.
The Seven Follies of Science [2nd ed.]
John Phin

British Dictionary definitions for perpetual motion

perpetual motion

noun

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
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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