In thermodynamics, Kräft (force) or Kräfte (forces) is the German word for force. The term ‘kraft’ is sometimes translated in English as energy and sometimes as power, although this may depend on context, in the same way the conservation of force differs subtly from the conservation of energy. The following is German chemist Karl Mohr‘s 1837 definition of Kraft: [1]

"Besides the fifty-four known chemical elements there is in the physical world one agent only, and this is called Kraft. It may appear, according to circumstances, as motion, chemical affinity, cohesion, electricity, light and magnetism; and from any one of these forms it can be transformed into any of the others."

To cite one example of a translation ambiguity, the founding paper of thermodynamics, the 1850 “Üeber die bewegende Kraft der Wärme und die Gesetze, welche sich daraus fur die Warmelehre selbst ableiten lassen” by Rudolf Clausius, has the main title “On the Moving Force of Heat” (Üeber die bewegende Kraft der Wärme), but some English reprints, e.g. Eric Mendoza (Dover, 1960), re-title this as “On the Motive Power of Heat”, thus translating Kraft as power, which does not seem to be a technically correct translation, although the meaning still comes across.

1. Mohr, K. F. (1837) "Ansichten über die Natur der Wärme" (“Views on the Nature of Heat”). Ann. der Pharm., 24, pp. 141–147.

Further reading
● Helmholtz, Hermann. (1847). “On the Conservation of Force”, “Uber die Erhaltung der Kraft”, presented at the meeting of the Physical Society of Berlin on July 23.

External links
Kraft (German → English) – Wikipedia.

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