Обозначения кинетической и потенцпальной энергий

[Michaele]

Почему повелось обозначать кинетическую энергию буквой "T", а потенциальную — буквой "U"?

[Slav-27]

Самое правдоподобное объяснение из тех, что нагуглились:

http://www.reddit.com/r/Physics/comments/52svbt/why_is_potential_energy_denoted_as_u писал(а):

I know that Lagrange himself used $T$ and $V$ for kinetic and potential energy. I dug through his flagship book Mécanique Analytique (published early 1800s) and the first mention of potential energy seems to be:

Цитата:

...et cette valeur de $S\Pi m$ étant nommée $V$, on aura immédiatement
$\delta V = \frac {d V}{d \xi} \delta \xi + \mathrm{etc.}$

Source, go to page 313
Basically, he just pulls the letter from nowhere and doesn't explain why. He's already used $S$ for the action, $T$ for kinetic energy ("forces vives"), and $U$ for the Lagrangian, so maybe he is just picking random letters from that part of the alphabet.