air volume formula?

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On 27 Oct 2003 11:57:00 -0800, gnygaard@nccray.com (Gene Nygaard) wrote:

>bullshark <bullshark@scubadiving.com> wrote in message news:<1l5qpv48hkj8fivob5iooa8rq9bptq5139@4ax.com>. ..
>>
>> The meter is the length of the path traveled by light in vacuum during a time interval
>> of 1/299,792,458 of a second?
>> That's not a historical accident? That's not arbitrary?
>
>The arbitrariness isn't in the definition of any particular unit,
>idiot.

Snappy response. You're pretty edgy. You don't like seeing how arbitrary
your basis is, and need to vent. Too bad you didn't read the next paragraph
before you blew your top. It makes you look kind of silly.

No further discussion will be entertained because as any schoolchild knows,
"I'm rubber, you're glue. Whatever you say bounces off me and sticks to you."

You should really try not to get all emotional about units. It's not
good for you.


>> The kilogram is equal to the mass of the international prototype of the kilogram.
>> I won't even ask where it came from. This is the evil stepmother for the whole system.
>> Why? 1000 cc's of distilled water better have a mass of 1 Kg. It's a bootstrap
>> nightmare about chickens, eggs, which came first, and why exactly a measurement
>> system should be based on a heap of stuff somewhere

>>
>> The whole thing is no different. It's arranged by treaty.
>>
>> The International foot, BTW is also defined by treaty. It is *precisely* .3048M.
>> Not "sort of", not "about", but *precisely* .3048M.
>
>No, it isn't. It is 0.3048 m. Learn the damn rules.

Spelling alert. You've lost the argument.

BTW, it's "damned" not "damn". Yer grammar's as poor as your attitude.

Chris Guynn <chrisguynn@sbcglobal.N.O.S.P.A.M.net> skriver:
>> >> 500m and serius time to get of the motorway. So far I have gotten but
>> >> I have no idea how long time it takes to drive 30 miles.
>> > At 30 miles an hour, it takes one hour. At 60 miles an hour it takes
> 1/2 an
>> > hour. Any other questions?
> Sure, but that's true no matter which system you use. Average speed is
> calculated the same regardless.

Sure and with some more time in this contry using these strange
messurments I might even get used to them.

> prefer, just divide by 1.5) and you should have an estimation of the number
> of km and can then guesstimate how long it will take.

Jep, by converting I can make a guess. However I'm have trobel
doing this while concentrations on driveing. But that probaly get
better by all the time. I know know what all the speedlimits are in
km/h so eventually I'll start to know what the distances are too.

> like speaking a second (non-native) language. Eventually, you don't have to
> interpret the words into your own language, you just understand them.

The basics was that the metric system is as easy or maybe easier that
the old imperial system. The systemt that you have started to use as
kid is the system that will feel the most natural at least untill you
have gotten very used to the other system. For me however it's more of
a problem that they drive on the wrong side of the road however. It's
so hard to see when getting ready for an overtake.

/ Balp
--
http://anders.arnholm.nu/ Keep on Balping

gnygaard@nccray.com (Gene Nygaard) wrote:

> bullshark <bullshark@scubadiving.com> wrote in message

> > >They are not a set of unconnected arbitary units, arrived at through
> > >historical accident.
> >
> > Are you sure about that?
> >
> > SI unit for time is the second.
> > The second is the duration of 9,192,631,770 periods of the radiation
> > corresponding to the
> > transition between the two hyperfine level of the ground state of the
> > cesium-133 atom.
> > That's not a historical accident? That's not arbitrary?
> >
> > The meter is the length of the path traveled by light in vacuum during a
> > time interval
> > of 1/299,792,458 of a second?
> > That's not a historical accident? That's not arbitrary?
>
> The arbitrariness isn't in the definition of any particular unit,
> idiot. It is in the relationships between different units for the
> same quantity.

The arbitrariness comes from the unit being defined by a legacy unit
which had been merely updated instead of redefined over the decades.

For example, a second doesn't have to be 9,192,631,770 cesium
vibrations, but if we were to, say, 'round it off' to a nice even 10
billion vibrations, then all of our time and navigation systems would
have to be rebuilt, because we would no longer have a 24:00 hour day.

Similarly, the meter wasn't redefined from a 1/299,792,458 light-second
to a 1/300,000,000 light-second because there already were physical
"reference meters" being used in trade and industry, usually located
right next to the previously distributed 'reference yardsticks'.

The point here is that the meter is a good example of theory vs.
practice, because while its invention may have started with a
theoretical scientific basis instead of the King's foot, at the time of
its invention, it could not be calculated very easily (or very
accurately, by today's standard; it doesn't help matters that the Earth
isn't quite a sphere as was assumed...).


> > The kilogram is equal to the mass of the international prototype of the
> > kilogram. I won't even ask where it came from...

The reference kilogram is defined by a platinum-iridium cylinder, cast
by a goldsmith in England in 1889. There were 80 of them made, and they
were distributed to various nations to use as physical constants.


I noticed Gene passed comment here, probably for very good reason:

Earlier this year, scientists reported a little problem: it has been
found that the reference kg has been shedding weight at a rate of 50
micrograms per year:

http://physics.csufresno.edu/wassign...l/Kilogram.htm



> The fact that all units are related by powers of 10 is in fact a
> pretty darned big benefit.

Yes, that's convenient for doing mathmatical conversions. But it
doesn't make the units themselves convenient for everyday use. For
example, both in the USA and in Europe, if you're in a market buying
something like cheese, the units that you'll make both orders in are
different, but the actual mass incriments used are roughly the same
(1/4lb, or 100g).



> The even bigger benefit is that it is an interdisciplinary and
> International System of Units.

That's merely paperwork for politicians...the units agreed upon are not
germain to the treaty and could just as easily been anything else.


> Any time you do a conversion between units not related by powers of
> 10, you lose something.

Which includes the perspective of what constitues significant digits for
the task at hand.


FWIW, don't get me wrong: I enjoy the SI system's benefits of being
able to slide around decimal points, and less confusing technical
Engineering units...mucking around with LBf vs LBm vs Stone, etc. But
just because one system looks "cleaner" than another overall does not
automatically make it superior for all possible tasks/applications.


-hh

PS for Anders: the pragmatic conversion of (miles:km) is a 5:8 ratio.

So 30 miles, 30/5 = 6, 6 * 8 = 48km.

Personally, I just remember 50 miles = 80km, 25mi=40km and similar
multiples when trying to convert back & forth. Here, since 30 miles is
just a bit more than 25mi (40km), I'd base whatever I'm doing on that.

~60mph is a pretty common highway speed, and this conveniently works out
to 1 mile/minute. City driving is 20-30mph and works out to 1 mile
every 2-3 minutes. You probably already do similar pragmatic
approximations with 30kph, 60kph and 120kph values.

So if I was going someplace and it was 5 more miles, on a highway, I'd
SWAG it as another 5 minutes....or if you prefer a more base unit,
approximately 2,757,789,531,002 cesium vibrations


-hh