A free particle has no potential energy, so its Hamiltonian is . On unbounded Euclidean space its energy spectrum has no normalizable lowest-energy eigenstate.
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A free particle is a concept in physics, particularly in classical mechanics and quantum mechanics, referring to a particle that is not subject to any forces other than its own inertial motion. This means that a free particle moves through space without any interaction with other particles or fields and is not influenced by any potential energy. ### In Classical Mechanics: In classical mechanics, a free particle moves in a straight line at a constant speed according to Newton's First Law of Motion.