In terms, vis viva (TR:102) (LH:7) (TL:109), from Latin vita meaning "living" or "life", + vis meaning "force", translates as "living force" (Leibniz, 1686); this term eventually became replaced by the terms: "moving force" (Joule, 1846), then "actual energy" (Rankine, 1853), and finally "kinetic energy" (Thomson, 1862).
In 1875, Rudolf Clausius, in his "Mathematical Introduction", of his Mechanical Theory of Heat (second edition), defined the energy U, aka "internal energy", of the "system" (aka "working body") as follows:
where T is the the "vis viva" and J is the "ergal".
The following are quotes:
- “The force expended in setting a body in motion is carried by the body itself, and exists with it and in it, throughout the whole course of its motion. This force possessed by moving bodies is termed by mechanical philosophers vis viva, or living force. The term may be deemed by some inappropriate, inasmuch as there is no life, properly speaking, in question; but it is useful, in order to distinguish the moving force from that which is stationary in its character, as the force of gravity.”
- Joule, James. (1847). “On Matter, Living Force, and Heat”, Lecture at St. Ann’s Church Reading room; in: Manchester Courier newspaper, May 5 and 12; in The Scientific Papers, Volume One (pg. 266). The Physical Society, Great Britain.
- Vis viva – Hmolpedia 2020.