# Tag Info

## Hot answers tagged terminology

7

The "shift in the meaning" refers to some attempts to reinterpret the terminology that were made by a metrological document, ISO 5725, in 2008. That may be described as a bureaucratic effort by a few officials – really bureaucrats of a sort – and as far as I know, the "shift in the meaning" hasn't penetrated to the community of professionals. The people ...

6

The more common names for what you are talking about are the abbreviated action $$S_0[q] := \int p \mathrm{d}q$$ versus the action $$S[q] := \int_{t_1}^{t_2}L(q,\dot q,t)\mathrm{d}t$$ Both are used in different formulations of classical mechanics, and deliver a different "flavor" of solutions. On both one can do variations calculus and obtains the ...

3

I like alemi's suggestion in a comment of crash density, by analogy with the linear "mass density" for a rod. Among other advantages, this frees up "crash rate" to mean the number of crashes per million hours driven. Alternatively you could invert the crash density to talk about the "mean distance between crashes."

2

Work. Potential energy exists because of some force that exists, and moving an object relative to that force causes work to be done. And by the work-energy theorem, the work done on an object is equal to the change in kinetic energy of that object.

2

"Frames" is not a unit of anything. A frame is a thing. FPS in Hertz measures frames in one second. More generally Hertz can be used as the unit of any "thing" per second. In the case of an oscillating wave we measure cycles per second in Hertz. When I was young, there was no "Hertz", and the units were "cps" and "fps". Those old designations were ...

2

As user ACuriousMind correctly writes: What Goldstein calls the principle of least action $\int p~\mathrm{d}q$ is usually called Maupertuis' principle or the principle of abbreviated action. What Goldstein calls the Hamilton's variational principle is often also called the the principle of least/extremal/stationary action $\int L~\mathrm{d}t$. This is ...

1

You could use the generic/boring term ratio, and precede it with CMK for crashers per million kilometers. The entire thing then becomes the CMK ratio. Though CMK rate can also work as others have said so long as your definition is clear. Then there's CMK factor if you want to use a fancier but more ambiguous term.

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Collider physicists actually use a quantity called "luminosity" which has inverse areal units, and they just quote as such (note that a "barn" is a (very small) measure of area), so when they say "inverse-femtobarns" they mean the inverse of an exceedingly small area which equates to a very high luminosity. There is nothing fundamentally wrong with "inverse ...

1

The term "Crash Recurrence" comes to mind. http://dictionary.reference.com/browse/recurrence an act or instance of recurring. return to a previous condition, habit, subject, etc. It captures the concept of an interval without implying that it is regular or predictable, which seems to be what you're looking for.

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The common definition of "time" is a type of measurement, like size. No. The common definition of "time", certainly in the context of physics, is as one indication of one participant, or also as the ordered set of all indications of one participant. As Einstein put it: "[... that instead] of "time" we substitute "the position of the little hand of my ...

1

I'm not familiar with ISO 5725 (a 1994 revision of a 1986 document, apparently "reviewed and confirmed" in 2012), and it seems that I have to buy it to read it. A 2008 vocabulary of metrology put out by the BIPM and also cited by Wikipedia has definitions much closer to my intuition, and to common usage among folks I know who specialize in precision ...

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