A proposed cyclic machine that continuously delivers useful work without the corresponding permitted energy input. A first-kind machine violates conservation of energy; a second-kind machine would turn heat from a single reservoir completely into work in a cycle, contrary to the Kelvin-Planck statement. Continuing ideal motion without withdrawing work is a different claim.
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Perpetual motion refers to the hypothetical concept of a machine or device that can operate indefinitely without an external energy source. Such a machine would be able to continuously perform work or produce energy without the need for fuel or input energy, effectively violating the laws of thermodynamics. There are two main types of perpetual motion: 1. **Perpetual Motion of the First Kind**: This type violates the first law of thermodynamics, which states that energy cannot be created or destroyed.