| 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. |
| perpetual motion n. The hypothetical continuous operation of an isolated mechanical device or other closed system without a sustaining energy source. |
perpetual motion
the action of a device that, once set in motion, would continue in motion forever, with no additional energy required to maintain it. Such devices are impossible on grounds stated by the first and second laws of thermodynamics.
Learn more about perpetual motion with a free trial on Britannica.com.
