Re: How far does an object fall during the first half second after it's released?
From: Gene Nygaard (gnygaard_at_nccray.com)
Date: 07/08/04
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Date: Thu, 08 Jul 2004 08:57:47 -0500
On 8 Jul 2004 04:46:32 -0700, dcshead@charter.net (Donald G. Shead)
wrote:
>The Ghost In The Machine <ewill@aurigae.athghost7038suus.net> wrote in message news:<5puir1-iel.ln1@lexi2.athghost7038suus.net>...
>CUT<
>>
>> SI is definitely better at keeping the concepts separate;
>> it turns out a 1 pound mass will exert 1 pound force on
>> Earth, leading to much confusion. A 1 kg mass, by contrast,
>> will exhibit a force of 9.805 Newtons, give or take -- and
>> is far easier to keep straight in my mind (and probably
>> others' minds as well).
>>
>Aren't you forgetting - if you even know - that the newton was thought
>up about a hundred years after the advent of the metric system?
Which was, of course, still 60 years before the advent of SI.
Furthermore, the dyne--an obsolete metric unit of force in a coherent
system of units--is 30 years older than the newton. One reason the
newton wasn't invented until the 20th century is that hardly anybody
used meter-kilogram systems before then.
>Originally it was thought, _and designed_(!) that a 1 kg mass exerted
>1 kg force on Earth,
False. Nobody worried about units of force when the metric system was
invented. There were no well-defined units of force anywhere in the
world at the time.
Here's one for all the people who like to think they are smarter than
Dense Donny. Isaac Newton liked to measure mass in troy ounces and
troy grains, and he liked to measure length in toises and pieds and
pouces, the old French units, though he sometimes used English inches
as well. So what did he use for units of force? Perhaps something
like troy ounce-toises per fortnight squared? Grain-inches per hour
per second?
The kilogram, like the various pounds it replaced, was then and
remains a unit of mass.
Of course, nobody could possibly have known what a kilogram of force
was, before the kilogram as a unit of mass was invented. That's so
obvious I wouldn't have to explain this simple fact to anybody not so
unbelievably stupid as you are, Donald.
>leading to much confusion:
No more confusion that pounds force cause.
Pounds force were never well defined units before the 20th century.
> Which lead to
>kilograms of mass and kilograms of force: Which is what led pounds
>force to pounds mass,
At least kilograms force were officially defined back in 1901.
That's more than you can say for pounds force, which have never been
officially defined.
>and the erroneous definition of a pound force as
>a fraction [0.45] of a kilogram: That's where you get your idea that
>"A 1 kg mass, by contrast, will exhibit a force of 9.805 Newtons, give
>or take -- and is far easier to keep straight in my mind (and probably
>others' minds as well)." That's true now, but it wasn't before the
>metric - now SI - newton was thought up:
But that's one of the biggest advantages of the metric system, Dense
Donny--it's still fully supported and updated.
Now is what matters, Chicolini!
The keepers of our standards have been telling us for 40-odd years to
stop using the kilogram force. In the unsupported and unupdated
English units, nobody will ever bother to tell us to stop using the
pound force without telling us not to use pounds of any sort.
The modern metric system (SI) has the advantage of having distinct
units for force and mass. Other metric systems which did not do that
are obsolete. Grams force and kilograms force are no longer
acceptable units. But there is no International English System of
Units, and both pounds and pounds force remain in common use.
Now is what matters in physics too, Dense Donny--and pounds of any
sort have disappeared from our physics textbooks, even in the United
States.
>The correct definition of 1 pound - force _or_ weight - is that it's a
>force equal to the _weight_ of 0.45... kilogram! Think in retrospect!
http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf
Since 1893 the National Bureau of Standards and its predecessor
agency, the Office of Standard Weights and Measures of the Treasury
Department, have derived the yard and the pound and the multiples and
submultiples of these units from metric standards, namely, the
international meter and the international kilogram. The original
announcement of this derivation, together with the numerical ratios
upon which the derivations were based, is given in Bulletin 26,
"Fundamental Standards of Length and Mass", of the U.S. Coast and
Geodetic Survey, approved for publication April 5, 1893, by the
Secretary of the Treasury. An amendment to the 1893 Bulletin was made
in 1894 in which there was a small adjustment in the pound-kilogram
ratio to bring it into closer agreement with the British Imperial
pound.
. . .
Announcement. Effective July 1, 1959, all calibrations in the U.S.
customary system of weights and measures carried out by the National
Bureau of Standards will continue to be based upon metric measurement
standards and, except those for the U.S. Coast and Geodetic Survey as
noted below, will be made in terms of the following exact equivalents
and appropriate multiples and submultiples:
1 yard= 0.914 4 meter
1 pound (avoirdupois)= 0.453 592 37 kilogram
Currently, the units defined by these same equivalents, which have
been designated as the International Yard and the International Pound,
respectively, will be used by the National Standards Laboratories of
Australia, Canada, New Zealand, South Africa, and United Kingdom; thus
there will be brought about international accord on the yard and pound
by the English-speaking nations of the world, in precise measurements
involving these basic units.
Gene Nygaard
Time flies like an arrow;
fruit flies like a banana.
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