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perpetual motion

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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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

  • 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.

  • 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.

  • Many inventors of perpetual-motion machines offer their poverty as an excuse for not making a model or working machine.

British Dictionary definitions for perpetual motion

perpetual motion

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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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012