Why discern Kinetic and Potential Energies? Say we have kinetic energy of the Moon, which prevents Moon's falling onto the Earth, while at the same time this kinetic energy makes potential energy, because some huge body, hitting the Moon, may spiral Moon into Earth. So Other example is water in a river, possesing kinetic energy, which becomes potential energy, if applied to a turbine. I think physical nomenclature is completely retarded.