ABSTRACT -/- Since Newton established the bases of classical mechanics, it has been readily accepted that statics is a chapter of physics. However, from Antiquity to the Renaissance the two disciplines, statics and dynamics, had different histories that only sometimes interacted with one another. In this article, part of this process is described whereby statics was established during Antiquity in rigorous and mathematical form, whereas dynamics confronted conceptual and empirical difficulties, which began to be clarified only in the Renaissance. The (...) laws of statics were initially established by Archimedes using a rigorous axiomatic system. It is shown that while there was a strong resurgence of the Archimedean tradition during the Renaissance, there was also a rival tradition that was, up to a point, disposed to sacrifice mathematical rigor, and instead make use of dynamical principles that have dubious foundation but that are heuristically efficacious. Galileo was a clear exponent of the new Renaissance culture interested in connecting the traditions of statics and dynamics; he considered it possible to give a rigorous and geometrical foundation to the study of movement, that enabled him to resolve the tension between statics and dynamics and to bring Renaissance mathematics to a successful realization that contributed to the birth of a new physics. -/- Keywords: Archimedes. Aristotelian physics. Galileo. Statics. Dynamics. Antiquity. Renaissance. Momentum. Lever. Inclined plane. (shrink)

Incontestablement, La conservation de la force d’Helmholtz constitue un texte qui annonce la conservation de l’énergie, comme en témoignent l’introduction du concept de potentiel, l’importance accordée au concept de travail ainsi que le fort degré de généralité du principe de conservation tel qu’il est exposé. Cependant, ce dernier présente certaines restrictions (statut des pertes, de la chaleur, formalisation mathématique...) qui empêchent la formulation du concept d’énergie totale. Nous montrons que c’est donc la conservation de l’énergie mécanique qu’il convient de lire (...) dans le texte d’Helmholtz. Ces restrictions sont significatives de l’attachement de ce dernier à une mécanique conservative qui rend parfaitement compte du principe fondateur de la théorie (l’impossibilité d’obtenir un mouvement perpétuel) et qui par ailleurs est cohérente avec ses travaux de physiologie. (shrink)