Science > Physics > Why the metric committee chose the kilogram as the standard mass
| Topic: |
Science > Physics |
| User: |
"Don1" |
| Date: |
26 Jun 2005 06:34:20 PM |
| Object: |
Why the metric committee chose the kilogram as the standard mass |
Why did the metric system choose the kilogram as the standad unit for
their new system of weights and measures? Its weight varies at various
locations; in proportion to the force of gravity, so that the ratio of
it's weight (w), to the acceleration (g) at which it will free fall is
a constant anytime, anywhere.
Don
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
26 Jun 2005 06:37:05 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119828860.620324.319940@f14g2000cwb.googlegroups.com...
Why did the metric system choose the kilogram as the standad unit for
their new system of weights and measures? Its weight varies at various
locations; in proportion to the force of gravity, so that the ratio of
it's weight (w), to the acceleration (g) at which it will free fall is
a constant anytime, anywhere.
Don
Did you get fed up with all the other threads you have here, saying the same
thing, where you are constantly being corrected.
Is some one paying you for each new thread you start?
Is there anything which doesn't have a weight that varies in proportion to
gravity?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 07:18:25 AM |
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T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119828860.620324.319940@f14g2000cwb.googlegroups.com...
Why did the metric system choose the kilogram as the standad unit for
their new system of weights and measures? Its weight varies at various
locations; in proportion to the force of gravity, so that the ratio of
it's weight (w), to the acceleration (g) at which it will free fall is
a constant anytime, anywhere.
Don
Did you get fed up with all the other threads you have here, saying the same
thing, where you are constantly being corrected.
If the corrections were correct, I'd have no recourse but to accept
them. Trouble is dopes like you keep getting off the subject with their
erroneous corrections as they try to lead me down the wrong path. I
have to start over to get back on track.
Is some one paying you for each new thread you start?
No. So far it's free.
Is there anything which doesn't have a weight that varies in proportion to
gravity?
Now you are getting the idea: AFAIK, there is nothing which doesn't
have a weight that varies in proportion to gravity.
Don
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| User: "Timothy" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
26 Jun 2005 11:25:59 PM |
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Why did the metric system choose the kilogram as the standad unit for
their new system of weights and measures?
I am not sure if the "metric system" can make choices. It is not a
sentient being. It is just a mathematical construct created by human
beings.
That said, some versions of the metric system do use the kilogram
(rather than the gram) as the fundamental unit of mass.
As I recall, the metre is the size it is because the earth's diameter
was estimated to be the equivalent of 40,000 km. The number 40,000,
however was chosen more or less arbitrarily so that the distance from
the equator to the North and South Poles would be 10,000,000 metres (or
10,000 km.) This just happens to yield a value more or less the same
length as the yard :-)
The gram was originally the mass of 1 cubic centimetre of water. The
kilogram was a thousands times that size, which corresponds to one
litre of water. One litre of water just happens to be more or less the
same size as a quart :-)
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| User: "" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
26 Jun 2005 07:05:25 PM |
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Because it's based on water just like the rest of the metric system -
a very easy to obtain and harmless substance to base a system on.
Would you prefer them to base it on unicorn feathers instead?
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| User: "Kac Demetrie" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
26 Jun 2005 08:19:15 PM |
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<abe.buckingham@gmail.com> wrote in message
news:1119830725.932932.258590@g43g2000cwa.googlegroups.com...
Because it's based on water just like the rest of the metric system -
a very easy to obtain and harmless substance to base a system on.
Would you prefer them to base it on unicorn feathers instead?
Also the measurement with water is very accurate and repeatable.
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| User: "tadchem" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 12:30:53 PM |
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At one time it was probably the best they could do.
Now we can do better. Now we can measure differences in the isotopic
composition of the "purest" water - conductivity grade H2O. A
*standard* cannot be subject to uncontrolled variabilities that make
measurable differences.
The continuing refinements in metrology drive the need for improvements
in the quality of our *standards*.
Tom Davidson
Richmond, VA
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 12:57:37 PM |
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tadchem wrote:
At one time it was probably the best they could do.
Now we can do better. Now we can measure differences in the isotopic
composition of the "purest" water - conductivity grade H2O. A
*standard* cannot be subject to uncontrolled variabilities that make
measurable differences.
The continuing refinements in metrology drive the need for improvements
in the quality of our *standards*.
Still there will always be manufacturing tolerences; due to human
abilities even by the most skilled professionals.
Don
Tom Davidson
Richmond, VA
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 08:07:29 AM |
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Kac Demetrie wrote:
<abe.buckingham@gmail.com> wrote in message
news:1119830725.932932.258590@g43g2000cwa.googlegroups.com...
Because it's based on water just like the rest of the metric system -
a very easy to obtain and harmless substance to base a system on.
Would you prefer them to base it on unicorn feathers instead?
Also the measurement with water is very accurate and repeatable.
That's what I thought Kac; but they tell me that real precision
requires something other than water. Newton invented mass as the
product of a body's bulk and density, but I don't think he mentioned
water.
Some have found that a liter of water is off from a kilogram by
something like 18 parts per million: So they redefined the liter.
Modern science requires greater precision.
Don
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| User: "" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 06:25:09 PM |
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Who tells you real precision requires something other then water? What
do you recommend instead?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
27 Jun 2005 07:02:44 PM |
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wrote:
Who tells you real precision requires something other then water? What
do you recommend instead?
I don't believe that you can find a more abundant and easier to work
substance than water: It can be weighed and its volume determined at
most pressures and temperatures obtainable in any ordinary laboratory.
In short, properly handled, I don't think you can beat water for making
precise quantities!
Don
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| User: "" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 03:59:25 AM |
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In article <1119916964.829857.325900@g43g2000cwa.googlegroups.com>,
"Don1" <dcshead@charter.net> wrote:
abe.buckingham@gmail.com wrote:
Who tells you real precision requires something other then water? What
do you recommend instead?
I don't believe that you can find a more abundant and easier to work
substance than water: It can be weighed and its volume determined at
most pressures and temperatures obtainable in any ordinary laboratory.
In short, properly handled, I don't think you can beat water for making
precise quantities!
How do you transfer that last drop? The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
/BAH
Subtract a hundred and four for e-mail.
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| User: "tadchem" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 11:31:57 AM |
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wrote:
<snip>
How do you transfer that last drop?
....touch the tip of the dispenser to the inside surface of the
receiver...
The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
Lower division chemistry students are no longer permitted to handle
mercury for the same reason that water does not make a suitable
substance for preparing high-precision standards - evaporation.
In the case of mercury it is because the vapors are hazardous. In the
case of water it is because a few picoliters lost to uncontrolled
evaporation can make a *measurable* difference.
Tom Davidson
Richmond, VA
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 05:51:13 PM |
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tadchem wrote:
jmfbahciv@aol.com wrote:
<snip>
How do you transfer that last drop?
...touch the tip of the dispenser to the inside surface of the
receiver...
The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
Lower division chemistry students are no longer permitted to handle
mercury for the same reason that water does not make a suitable
substance for preparing high-precision standards - evaporation.
In the case of mercury it is because the vapors are hazardous. In the
case of water it is because a few picoliters lost to uncontrolled
evaporation can make a *measurable* difference.
That's why we do this in the controlled environment of a laboratory: To
control evaporation, and the temperature and pressure of the whole
process.
Don
Tom Davidson
Richmond, VA
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| User: "Clemens W" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 07:54:43 AM |
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Don, the 19th century physicist, wrote:
That's why we do this in the controlled environment of a laboratory: To
control evaporation, and the temperature and pressure of the whole
process.
Don, you don't even see a circular reference when it's running circles
around your head, do you?
The definition of 1 kilogram as "the mass (not the weight!) of 1 litre
of pure water at 4=B0C and standard atmospheric pressure (i.e. 101.325
kilopascals (kPa) or 2116.2 pounds-force per square foot (lbf/ft=B2))
was abandoned 100+ years ago. Why?
Water is slightly compressible, so the density of water depends on
(atmospheric) pressure. Pressure is force per area. Force is mass times
acceleration.
So, how do you want to measure someting when the measured object
depends on the measured unit?
Your turn,
A=2E Friend
--
DON'S MATHEMATICAL BLUNDERS, ERRORS and FALLACIES
Date Don Correct
12/06 g=3D(vt-vi)/t^2 g=3D(vt-vi)/t
12/06 (m)=3Dft/s/t m=3DFt^2/2s
07/06 (m)=3Dwa/fg m=3DF/a or m=3Dw/g
28/05 1 slug =3D 32 ft sec^2/32 ft 1 slug =3D 32 lbf sec^2/32 ft
27/05 s=3D2(vt-vi)/t s=3D1/2(vt-vi)*t
And, best of all:
21/05 1 slug =3D 1 lbf s^2/foot; _Not_ 1 slug =3D 1 lbf / (1 ft/s^2)
Don didn't even realize both equations are the same.
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| User: "The Ghost In The Machine" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 10:00:03 AM |
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In sci.math, Clemens W
<a.friend@bigfoot.com>
wrote
on 29 Jun 2005 05:54:43 -0700
<1120049683.905404.154780@o13g2000cwo.googlegroups.com>:
Don, the 19th century physicist, wrote:
That's why we do this in the controlled environment of a laboratory: To
control evaporation, and the temperature and pressure of the whole
process.
Don, you don't even see a circular reference when it's running circles
around your head, do you?
The definition of 1 kilogram as "the mass (not the weight!) of 1 litre
of pure water at 4°C and standard atmospheric pressure (i.e. 101.325
kilopascals (kPa) or 2116.2 pounds-force per square foot (lbf/ft²))
was abandoned 100+ years ago. Why?
Water is slightly compressible, so the density of water depends on
(atmospheric) pressure. Pressure is force per area. Force is mass times
acceleration.
So, how do you want to measure someting when the measured object
depends on the measured unit?
By dividing the weight by the acceleration of gravity, of course! :-)
Never mind that (AIUI) g varies by about 0.4% or so across the
Earth's surface, never mind that since historical times the
usage of *torques* over *forces* to determine weight equality,
and therefore mass equality, has been used in the pan scale,
never mind that he's been proven wrong more times than the
number of milligrams in the Space Shuttle (OK, so the last might
be a *little* exaggerated)... :-)
Personally, I think it's possible to use a reference
force (given bases in length and temperature), but very
complicated. Something along the following lines:
[1] Build a large chamber, with a smaller chamber and piston. This
large chamber would have controlled pressure and temperature,
and be of known volume. It of course wouldn't leak.
Ideally it would be absolutely rigid; of course that's
not possible.
[2] Build a smaller piston with two feeds; the volume of the
piston within the large chamber, and the sum of the volumes
of the two areas on each side of the piston, are known.
The (outside) volume of the piping would ideally be known as well,
and of course the piston wouldn't leak.
[3] Evacuate the outer chamber as well as able, then introduce a known
quantity of gas thereinto. (This quantity would be determined
by the gas's volume when liquid. Granted, this has the same problem
as your method, as the volume would have to be determined
*outside* the large chamber and we've not defined pressure yet.)
[4] Evacuate the one piston chamber as well as able (by sweeping
the piston and using a vacuum pump), then introduce a known
quantity of gas thereinto.
[5] Evacuate the other piston chamber, then introduce a known
quantity of gas thereinto. Note at this point that we have
(or should have) equal pressures on both sides, as the
piston is allowed to move freely.
[6] Let everything thermally stabilize to a known temperature.
(In other words, break for lunch.)
[7] At this point the fish scale [*] is hooked up to the piston, and
then some more gas is introduced to the appropriate side,
to introduce a certain force. This can then be checked against
the fish scale.
Ta-daah! Except for the imprecision of the liquid volume
measurement, the main chamber measurement, and the piston
chamber measurement, the compensation required for various
temperature effects as gas is moved around, piston
leakage, main chamber leakage, and the general energy
required (vacuum evacuation and heat of vaporization of
the liquid, which would probably be diatomic nitrogen) --
it's perfect. :-)
An alternate possibility would involve the fabrication of
a pure iron spring of known dimensions, then evaluating
its force against the scale under test. (Note that
the introduction of carbon into the iron modifies the
stiffness. There's also probably a *lot* of issues
regarding the exact treatment of the iron as it cools --
I know of water-quenching and oil-quenching but am not
that experienced in metallurgy.)
Compare either method to a simple pan scale used to check to
see whether two masses are equal.
[1] Put weight A in pan A, and weight B in pan B. Check for balance.
[2] Put weight A in pan B, and weight B in pan A. Check for balance.
Because the pan scale uses *torque* (the pans exert a force on a
movable balance-arm) there are some issues in construction but
the above procedure will check the scale's honesty; the sensitivity
of the scale depends on the length of the balance-arms, and the
length of the indicator pointer attached thereto. There is the
possibility of variations in g between the pans but given the size
of most scales that's extremely minor.
Apart perhaps from the lever it's one of the simplest
machines in the Universe, and one could make a good
claim it *is* a lever, with some additional "hardware
modules" (the pans and the balance indicator) attached.
It can be constructed from just about any material that's
sufficiently rigid (someone's probably made one out of ice,
though the tensile strength thereof would preclude weighing
overly heavy items).
The main source of error might be flex in the balance-arms.
Small wonder SI standardized on mass, and not on force.
Your turn,
A. Friend
--
DON'S MATHEMATICAL BLUNDERS, ERRORS and FALLACIES
Date Don Correct
12/06 g=(vt-vi)/t^2 g=(vt-vi)/t
12/06 (m)=ft/s/t m=Ft^2/2s
07/06 (m)=wa/fg m=F/a or m=w/g
28/05 1 slug = 32 ft sec^2/32 ft 1 slug = 32 lbf sec^2/32 ft
27/05 s=2(vt-vi)/t s=1/2(vt-vi)*t
And, best of all:
21/05 1 slug = 1 lbf s^2/foot; _Not_ 1 slug = 1 lbf / (1 ft/s^2)
Don didn't even realize both equations are the same.
[*] a simple spring-like affair that uses Hooke's law to determine the
force, commonly used for weighing fish.
--
#191,
It's still legal to go .sigless.
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| User: "Clemens W" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
30 Jun 2005 09:25:30 AM |
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The Ghost In The Machine wrote:
By dividing the weight by the acceleration of gravity, of course! :-)
LOL! Are you trying to imitate Don or what?
Personally, I think it's possible to use a reference
force (given bases in length and temperature), but very
complicated. Something along the following lines:
[...snip...]
Whoa, couldn't you come up with something less mind-boggling? My brain
still hurts ;-)
Ta-daah! Except for the imprecision of the liquid volume
measurement, the main chamber measurement, and the piston
chamber measurement, the compensation required for various
temperature effects as gas is moved around, piston
leakage, main chamber leakage, and the general energy
required (vacuum evacuation and heat of vaporization of
the liquid, which would probably be diatomic nitrogen) --
it's perfect. :-)
So, perfect, like in, err, let's say perfect precision?
Good luck,
A. Friend
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 06:34:33 AM |
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wrote:
In article <1119916964.829857.325900@g43g2000cwa.googlegroups.com>,
"Don1" <dcshead@charter.net> wrote:
abe.buckingham@gmail.com wrote:
Who tells you real precision requires something other then water? What
do you recommend instead?
I don't believe that you can find a more abundant and easier to work
substance than water: It can be weighed and its volume determined at
most pressures and temperatures obtainable in any ordinary laboratory.
In short, properly handled, I don't think you can beat water for making
precise quantities!
How do you transfer that last drop?
That _can_ be a problem, and it depends if it's a big droopy thing, or
just a tiny needle point drip; as well as how steady your hands are. A
well controled shake might suffice: Or a strand of absorbant fiber.
The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
Mercury is fun to handle, but not good for fish.
Don
/BAH
Subtract a hundred and four for e-mail.
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| User: "Steve Ralph" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 09:52:20 AM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119958473.572299.167340@g47g2000cwa.googlegroups.com...
jmfbah...@aol.com wrote:
In article <1119916964.829857.325900@g43g2000cwa.googlegroups.com>,
"Don1" <dcshead@charter.net> wrote:
abe.buckingham@gmail.com wrote:
Who tells you real precision requires something other then water? What
do you recommend instead?
I don't believe that you can find a more abundant and easier to work
substance than water: It can be weighed and its volume determined at
most pressures and temperatures obtainable in any ordinary laboratory.
In short, properly handled, I don't think you can beat water for making
precise quantities!
How do you transfer that last drop?
That _can_ be a problem, and it depends if it's a big droopy thing, or
just a tiny needle point drip; as well as how steady your hands are.
It is almost impossible to get rid of that last drop, thats why we wear
underpants, letting it evaporate is usually impractical and leads to arrest
LOL
sr
A
well controled shake might suffice: Or a strand of absorbant fiber.
The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
Mercury is fun to handle, but not good for fish.
Don
/BAH
Subtract a hundred and four for e-mail.
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 07:17:30 AM |
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Don1 wrote:
jmfbah...@aol.com wrote:
In article <1119916964.829857.325900@g43g2000cwa.googlegroups.com>,
"Don1" <dcshead@charter.net> wrote:
abe.buckingham@gmail.com wrote:
Who tells you real precision requires something other then water? What
do you recommend instead?
I don't believe that you can find a more abundant and easier to work
substance than water: It can be weighed and its volume determined at
most pressures and temperatures obtainable in any ordinary laboratory.
In short, properly handled, I don't think you can beat water for making
precise quantities!
How do you transfer that last drop?
That _can_ be a problem, and it depends if it's a big droopy thing, or
just a tiny needle point drip; as well as how steady your hands are. A
well controled shake might suffice: Or a strand of absorbant fiber.
The only liquid that is
nice to handle is mercury but my experience is only Chem201
labs.
Mercury is fun to handle, but not good for fish.
Don
/BAH
Subtract a hundred and four for e-mail.
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Don
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| User: "Richard Henry" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 09:21:40 AM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 03:32:46 PM |
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Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 04:35:57 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119990766.394197.237880@g43g2000cwa.googlegroups.com...
Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
Isn't the weight of an object equal to its (density times volume) times
gravity? If either way it is negligible how can it's effect depend on which
one you are talking about?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 05:38:59 PM |
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T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119990766.394197.237880@g43g2000cwa.googlegroups.com...
Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
Isn't the weight of an object equal to its (density times volume) times
gravity? If either way it is negligible how can it's effect depend on which
one you are talking about?
Either way, the difference is negligible; whether you use mass-density,
or weight-density.
Don
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 03:08:58 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119998339.853904.75320@o13g2000cwo.googlegroups.com...
T Wake wrote:
Either way, the difference is negligible; whether you use mass-density,
or weight-density.
Don
Surely difference between weight-density and mass-density should be
significant. Using your own logic, isn't density more of a fundamental value
than weight?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
28 Jun 2005 05:52:14 PM |
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T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119990766.394197.237880@g43g2000cwa.googlegroups.com...
Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
Isn't the weight of an object equal to its (density times volume) times
gravity? If either way it is negligible how can it's effect depend on which
one you are talking about?
Either way, the difference is negligible; whether you use mass-density,
or weight-density.
Don
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 03:10:46 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1119999134.278720.131670@g14g2000cwa.googlegroups.com...
T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119990766.394197.237880@g43g2000cwa.googlegroups.com...
Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
Isn't the weight of an object equal to its (density times volume) times
gravity? If either way it is negligible how can it's effect depend on
which
one you are talking about?
Either way, the difference is negligible; whether you use mass-density,
or weight-density.
Don
By the way, have you shown a worked example of the figures for f=wa/g yet?
Would you like me to work through it?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 03:57:31 PM |
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T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119999134.278720.131670@g14g2000cwa.googlegroups.com...
T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119990766.394197.237880@g43g2000cwa.googlegroups.com...
Richard Henry wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1119961050.036476.158040@o13g2000cwo.googlegroups.com...
Oh yeah, I forgot to mention: that last drop could be allowed to
evaporate; by natural causes or by hot air.
Won't that affect the measurement?
It depends if you're talking about volume or weight. Either way it's
negligible.
Don
Isn't the weight of an object equal to its (density times volume) times
gravity? If either way it is negligible how can it's effect depend on
which
one you are talking about?
Either way, the difference is negligible; whether you use mass-density,
or weight-density.
Don
By the way, have you shown a worked example of the figures for f=wa/g yet?
Would you like me to work through it?
No thanks.
Don
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 03:58:49 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1120078651.585837.158070@g47g2000cwa.googlegroups.com...
T Wake wrote:
By the way, have you shown a worked example of the figures for f=wa/g
yet?
Would you like me to work through it?
No thanks.
Don
Ok. Can you show me how your figures work out then?
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| User: "Don1" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 05:11:09 PM |
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T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1120078651.585837.158070@g47g2000cwa.googlegroups.com...
T Wake wrote:
By the way, have you shown a worked example of the figures for f=wa/g
yet?
Would you like me to work through it?
No thanks.
Don
Ok. Can you show me how your figures work out then?
Nope.
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| User: "T Wake" |
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| Title: Re: Why the metric committee chose the kilogram as the standard mass |
29 Jun 2005 05:24:13 PM |
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"Don1" <dcshead@charter.net> wrote in message
news:1120083069.596201.143700@z14g2000cwz.googlegroups.com...
T Wake wrote:
"Don1" <dcshead@charter.net> wrote in message
news:1120078651.585837.158070@g47g2000cwa.googlegroups.com...
T Wake wrote:
By the way, have you shown a worked example of the figures for f=wa/g
yet?
Would you like me to work through it?
No thanks.
Don
Ok. Can you show me how your figures work out then?
Nope.
Ok. So f=ma, which actually works when you include numbers, is better than
your f=wa/g?
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