Velocity is to speed as acceleration is to ________?
In English, it seems that:
- Position is a vector. Distance/length is a name of its magnitude.
- Velocity is a vector. Speed is a name of its magnitude.
- Acceleration is a name of a vector and its magnitude.
- Force is a name of a vector and its magnitude.
- Momentum is a name of a vector and its magnitude.
Velocity/speed as well as position/length seem to be exceptions. The general trend is to not have different names for the scalar-forms of vectors.
In fact, I asked why this is the case on the History of Science and Math SE site a few months ago.
The answer told me that Gibbs and Wilson formally defined the difference between speed/velocity in technical English in 1901 in their book Vector Analysis:
Velocity is a vector quantity. Its direction is the direction of the tangent of the curve described by the particle. The term speed is used frequently to denote merely the scalar value of the velocity. This convention will be followed here.
Since then, others continued this trend and it eventually got settled. Before then, the distinction was less clear.
In other languages, there is not necessarily such a distinction. It is consensus in English, Spanish, my mother-tongue Danish and others, but not in Russian, German etc.
g-force is typically used to express the magnitude only, but the words are generally used interchangeably; laymen typically referring to the magnitude only.