# Vis viva

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).

## Overview

In 1686, Gottfried Leibniz introduced the term “vis viva”, into physics dialogue, as the quantity of the mass m of a moving object and the square of its velocity v, as follows:

${\displaystyle {\text{vis viva}}=mv^{2}}$

This was a parallel to the term “vis mortua” or dead force.

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:

${\displaystyle U=T+J}$

where T is the the "vis viva" and J is the "ergal".

## Quotes

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.”
James Joule (1847), “On Matter, Living Force [Vis Viva], and Heat” (pg. #) [1]