| Topic: |
Science > Physics |
| User: |
"Donald G. Shead" |
| Date: |
15 Apr 2004 08:00:14 AM |
| Object: |
Mass versus Weight |
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse, because here on Earth, mass and
weight both free fall at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Newton discovered the same thing a few years later by using
mathematics: He found that the velocity of free fall changed at a
constant rate; from an initial velocity [vi] to another velocity [vt],
during a period of time [2t]: Sothat [(vt-vi)/(2t) = about 16'/sec^2].
The difference between mass and weight is that ANY volume of the
material substance that we call matter is a "mass"! Weight is the
force that any gravitating mass exerts on terra firma, and/or a
support thereon.
Here on Earth, the weight of this mass is the magnitude of the force
with which we _measure_ it; which varies in proportion to the "bulk
and density conjointly"; of the mass.
A heavier mass is heavier in that it requires more force to support it
and move it around.
Using the ratios: mass = w/g = weight/(32'/sec^2), and weight-density
= weight/cubic foot; we find that the mass of a cubic foot of water is
62.42 pounds/(32.174feet/sec^2) = 1.94 pounds/(foot/sec^2); OR 1.94
"slug".
The weight-density of a cubic foot of water is 62.42 pounds per cubic
foot.: So that 1 pound/(62.42 pounds/cubic foot) = 0.01602 cubic foot;
conversely, the weight of 0.01602 cubic foot of water weighs almost a
pound: 0.01602 x 64.2 = 0.99965 pound!
A pound of water weighs 16 ounces, and occupies a volume of about
0.02602 cubic foot.
Mass is a quantity of matter; but is neither its weight nor bulk
alone; but is its bulk and weight-density ‘conjointly'.
Rev. 4/11/04 ds
It's much easier to "break the sound barrier", than to break the light
barrier: In fact it is impossible to break the light barrier because
there are no material particles of matter that are fast enough to
"throw through" it.
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| User: "Uncle Al" |
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| Title: Re: Mass versus Weight |
15 Apr 2004 09:24:33 AM |
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"Donald G. Shead" wrote:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
[snip]
1) Dumb Donny ***** STILL does not know the differences among
inertial, gravitational, active, and passive masses.
2) Dumb Donny ***** is a spewing idiot who cannot be educated in
high school physics.
3) Hey Dumb Donny *****, F=ma and F=GmM/r^2.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "Donald G. Shead" |
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| Title: Re: Mass versus Weight |
15 Apr 2004 04:25:44 PM |
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Uncle Al <UncleAl0@hate.spam.net> wrote in message news:<407E9B21.83D30A04@hate.spam.net>...
Cut<
Told ya once Unky Dukapuka: m = f/a = w/g; so f = wa/g; where f =
F-uw.
F=ma and F=GmM/r^2 are both wrong. Don't you know anything about
parentheses?
Maybe somebody from sci.math will have to explain it to you
Incidentally don't gimme that crap about relativity and speed
affecting mass. It isn't so:
Position and speed are relative to the positions and speeds of the
observers.
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| User: "Gene Nygaard" |
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| Title: Re: Mass versus Weight |
15 Apr 2004 05:04:00 PM |
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On 15 Apr 2004 14:25:44 -0700, (Donald G. Shead)
wrote:
F=ma and F=GmM/r^2 are both wrong. Don't you know anything about
parentheses?
Maybe somebody from sci.math will have to explain it to you
Thanks for the reminder that you really are every bit as stupid as you
appear to be. People do slip of every once in a while, forgetting
this basic fact which must guide any attempts at discussion with you.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
Gentlemen of the jury, Chicolini here may look like an idiot,
and sound like an idiot, but don't let that fool you: He
really is an idiot.
Groucho Marx
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| User: "Squishua" |
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| Title: Re: Mass versus Weight |
15 Apr 2004 09:24:10 PM |
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On 15 Apr 2004 14:25:44 -0700, (Donald G. Shead)
wrote:
[snip]
F=ma and F=GmM/r^2 are both wrong. Don't you know anything about
parentheses?
Learn something about the order of arithmatic operations before you
assume that parentheses are required. In the above examples, they are
not.
Regards,
Squishua
sqSuPiAsMhua@hotmail.com
(remove the capital letters from my e-mail address to contact me)
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| User: "G=EMC^2 Glazier" |
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| Title: Re: Mass versus Weight |
16 Apr 2004 07:29:44 PM |
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We can't possibly going over this again?????? Bert
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| User: "Sam Wormley" |
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| Title: Re: Mass versus Weight |
15 Apr 2004 08:38:00 AM |
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"Donald G. Shead" wrote:
Mass and weight are easy to confuse... [says Shead]
Sigh!
Inertia
http://scienceworld.wolfram.com/physics/Inertia.html
Weight
http://scienceworld.wolfram.com/physics/Weight.html
Mass
http://scienceworld.wolfram.com/physics/Mass.html
"The time has come," the Walrus said, "To talk of many things:
Of shoes, and ships, and sealing wax, of cabbages and kings.
And why the sea is boiling hot and whether pigs have wings."
Makes about as much sense as Shead eternal struggle with inertia,
weight and mass.
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| User: "ZZBunker" |
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| Title: Re: Mass versus Weight |
18 Apr 2004 07:49:16 AM |
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(Donald G. Shead) wrote in message news:<48402bae.0404150500.55bae6f5@posting.google.com>...
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse, because here on Earth, mass and
weight both free fall at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Newton discovered the same thing a few years later by using
mathematics: He found that the velocity of free fall changed at a
constant rate; from an initial velocity [vi] to another velocity [vt],
during a period of time [2t]: Sothat [(vt-vi)/(2t) = about 16'/sec^2].
The difference between mass and weight is that ANY volume of the
material substance that we call matter is a "mass"! Weight is the
force that any gravitating mass exerts on terra firma, and/or a
support thereon.
That's hardly true. Since the whole reason that
Einstone invented Special Relativity is to
tell mathemadorks, that that is *NOT TRUE* MORONS.
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| User: "The Ghost In The Machine" |
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| Title: Re: Mass versus Weight |
17 Apr 2004 07:00:43 PM |
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In sci.math, Donald G. Shead
<dcshead@charter.net>
wrote
on 15 Apr 2004 06:00:14 -0700
<48402bae.0404150500.55bae6f5@posting.google.com>:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
For idiots, maybe. Most people can tell the diff.
because here on Earth, mass and weight both free fall
at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Erm...if one has a mass and one has a weight, then one has
two objects of indeterminate mass and weight.
Ponder that for a moment.
As it is, units of mass are different from units of weight,
although most laypeople confuse the two.
But then, the obvious conclusion is that most laypeople are idiots. :-)
You are correct in that Galileo did careful measurement; that is
one of the foundations of science.
Newton discovered the same thing a few years later by using
mathematics: He found that the velocity of free fall changed at a
constant rate; from an initial velocity [vi] to another velocity [vt],
during a period of time [2t]: Sothat [(vt-vi)/(2t) = about 16'/sec^2].
You're confusing yourself. Mind you, I'd have to look as to exactly
what Newton did -- apart from composing such things as
_Principia Mathematica_, admittedly, which I've not read.
The difference between mass and weight is that ANY volume of the
material substance that we call matter is a "mass"! Weight is the
force that any gravitating mass exerts on terra firma, and/or a
support thereon.
Well, you've got that more or less right, except that it's not
quite general enough. Any two masses will exhibit a force.
Take two 50 kg masses (1 male, 1 female) and space them 1 m apart,
and the gravitational attraction will be about 1.67 * 10^-7 Newton,
or perhaps 1.67 * 10^-2 dynes might be a better method of expression.
Space them 1 cm apart and the attraction grows to 1.67 * 10^-3 Newton,
very roughly -- the problem is that people are't point masses so one
has to integrate over both volumes.
(The sexual attraction may be far higher but that's beyond the
realm of theoretical physics.)
Here on Earth, the weight of this mass is the magnitude of the force
with which we _measure_ it; which varies in proportion to the "bulk
and density conjointly"; of the mass.
And the mass of the Earth. On the Moon, the weight woudl be lighter.
A heavier mass is heavier in that it requires more force to support it
and move it around.
Using the ratios: mass = w/g = weight/(32'/sec^2), and weight-density
= weight/cubic foot; we find that the mass of a cubic foot of water is
62.42 pounds/(32.174feet/sec^2) = 1.94 pounds/(foot/sec^2); OR 1.94
"slug".
The weight-density of a cubic foot of water is 62.42 pounds per cubic
foot.: So that 1 pound/(62.42 pounds/cubic foot) = 0.01602 cubic foot;
conversely, the weight of 0.01602 cubic foot of water weighs almost a
pound: 0.01602 x 64.2 = 0.99965 pound!
A pound of water weighs 16 ounces, and occupies a volume of about
0.02602 cubic foot.
And this seems somehow "natural" to you? At least with the MKI system
a liter of water is close to a kg. :-)
Mass is a quantity of matter; but is neither its weight nor bulk
alone; but is its bulk and weight-density ‘conjointly'.
Rev. 4/11/04 ds
It's much easier to "break the sound barrier", than to break the light
barrier: In fact it is impossible to break the light barrier because
there are no material particles of matter that are fast enough to
"throw through" it.
Not sure I follow that logic, though the observation is correct.
--
#191,
It's still legal to go .sigless.
.
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| User: "Gene Nygaard" |
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| Title: Re: Mass versus Weight |
18 Apr 2004 12:12:47 PM |
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On Sun, 18 Apr 2004 00:00:43 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Donald G. Shead
<dcshead@charter.net>
wrote
on 15 Apr 2004 06:00:14 -0700
<48402bae.0404150500.55bae6f5@posting.google.com>:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
For idiots, maybe. Most people can tell the diff.
because here on Earth, mass and weight both free fall
at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Erm...if one has a mass and one has a weight, then one has
two objects of indeterminate mass and weight.
Ponder that for a moment.
As it is, units of mass are different from units of weight,
although most laypeople confuse the two.
But then, the obvious conclusion is that most laypeople are idiots. :-)
Hey, Ghostie, I bet if you revealed yourself, we could find out who
the idiots are!
In other words, tell us what you think some units are--nail down your
position, not just some vague bitching.
I'll bet you aren't any smarter than Shead and Uncle Al. What about
those troy pounds Uncle Al was talking about earlier this week in
another thread on sci.physics and alt.sport.hockey.nhl.det-redwings,
are they units of mass or units of force?
Avoirdupois pound--mass or force?
Short hundredweight--mass or force?
U.S. fluid ounce--mass or force?
Kilogram--mass or force?
Poundal--mass or force?
Hyl--mass or force?
Slug--mass or force?
Pennyweight--mass or force?
Slinch (1 lbf s²/in)-- mass or force?
Well, you've got that more or less right, except that it's not
quite general enough. Any two masses will exhibit a force.
Take two 50 kg masses (1 male, 1 female) and space them 1 m apart,
and the gravitational attraction will be about 1.67 * 10^-7 Newton,
or perhaps 1.67 * 10^-2 dynes might be a better method of expression.
Better?
So, you don't accept the authority of the BIPM and the NIST and every
other standards-setting agency to tell you to quit using dynes.
Do you object to the use of kilograms force? If so, please explain on
what authority you do so, if nobody has the authority to tell you to
quit using dynes.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
.
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| User: "The Ghost In The Machine" |
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| Title: Re: Mass versus Weight |
19 Apr 2004 11:00:22 AM |
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In sci.math, Gene Nygaard
<gnygaard@nccray.com>
wrote
on Sun, 18 Apr 2004 12:12:47 -0500
<dvc580tt1irv461r272lh4sg3bl1jhnkhq@4ax.com>:
On Sun, 18 Apr 2004 00:00:43 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Donald G. Shead
<dcshead@charter.net>
wrote
on 15 Apr 2004 06:00:14 -0700
<48402bae.0404150500.55bae6f5@posting.google.com>:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
For idiots, maybe. Most people can tell the diff.
because here on Earth, mass and weight both free fall
at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Erm...if one has a mass and one has a weight, then one has
two objects of indeterminate mass and weight.
Ponder that for a moment.
As it is, units of mass are different from units of weight,
although most laypeople confuse the two.
But then, the obvious conclusion is that most laypeople are idiots. :-)
Hey, Ghostie, I bet if you revealed yourself, we could find out who
the idiots are!
In other words, tell us what you think some units are--nail down your
position, not just some vague bitching.
By all means, have some units.
Mass: kg.
Weight: Newtons.
Length: meters
Pressure: Pascal (Newtons/m^2)
Time: seconds
Speed: m/s
Acceleration: m/s/s or m/s^2
Force: Newtons (same as weight).
A mass of 1 kg presses down on the hand with a force of 9.80665 Newtons,
more or less, on Earth. This "conversion" factor is quite variable
(it depends among other things on what planet one is on and how
high above the center one is), and a more reliable conversion was
initially attempted (AFAIK, mostly successfully; subsequent attempts
have improved the value) to find G in the formula
F = G * M * m/r^2
which is an idealization anyway (a better formula would use an
integral over the mass of the Earth) but works for simpler stuff.
G in this case is 6.6873 * 10^-11 m^3 / (kg * s^2). M is the
mass of the Earth, which is about 5.976 * 10^24 kg. d is the
radius of the Earth, which is 6.378*10^6 m. Plugging in
these values gives a g' of 9.824, so my units aren't all that
consistent.
I'll forbear angular measurements as I'm not all that familiar
with them beyond noting that radians is an important component
thereof. (1 radian is the angle subtending 1m of circumference
on a circle of radius 1m. It's just shy of 60 degrees.)
I'll bet you aren't any smarter than Shead and Uncle Al. What about
those troy pounds Uncle Al was talking about earlier this week in
another thread on sci.physics and alt.sport.hockey.nhl.det-redwings,
are they units of mass or units of force?
Mass.
Avoirdupois pound--mass or force?
Mass.
Short hundredweight--mass or force?
Mass, most likely.
U.S. fluid ounce--mass or force?
Neither; it's a unit of volume.
Kilogram--mass or force?
Mass.
Poundal--mass or force?
Force.
Hyl--mass or force?
I'd have to look. Google suggests 1 Hyl = 9.80665 kg.
Therefore, mass.
Slug--mass or force?
Mass.
Pennyweight--mass or force?
Most likely mass.
Slinch (1 lbf s²/in)-- mass or force?
That is one strange unit. Looks like it might be mass
(1 N = 1 kg * m / s / s; therefore 1 kg = 1 N * s * s / m)
but strangely expressed. (It came through as \262 on my
viewer, which didn't help; presumably that's '^2'.)
Well, you've got that more or less right, except that it's not
quite general enough. Any two masses will exhibit a force.
Take two 50 kg masses (1 male, 1 female) and space them 1 m apart,
and the gravitational attraction will be about 1.67 * 10^-7 Newton,
or perhaps 1.67 * 10^-2 dynes might be a better method of expression.
Better?
So, you don't accept the authority of the BIPM and the NIST and every
other standards-setting agency to tell you to quit using dynes.
I use Newtons because it's part of SI. Dynes are part of cgi, an
older standard but still useful. Better in that the human mind relates
a little more easily to 0.0167 than 0.000000167, and in any event,
it's fairly small.
Do you object to the use of kilograms force? If so, please explain on
what authority you do so, if nobody has the authority to tell you to
quit using dynes.
If one has a precise definition of kg-f, then by all means use it.
I even have a conversion-factor: 1 kg-f = 9.80665 N.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
--
#191,
It's still legal to go .sigless.
.
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| User: "Gene Nygaard" |
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| Title: Re: Mass versus Weight |
19 Apr 2004 11:26:12 AM |
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On Mon, 19 Apr 2004 16:00:22 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Gene Nygaard
<gnygaard@nccray.com>
wrote
on Sun, 18 Apr 2004 12:12:47 -0500
<dvc580tt1irv461r272lh4sg3bl1jhnkhq@4ax.com>:
On Sun, 18 Apr 2004 00:00:43 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Donald G. Shead
<dcshead@charter.net>
wrote
on 15 Apr 2004 06:00:14 -0700
<48402bae.0404150500.55bae6f5@posting.google.com>:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
For idiots, maybe. Most people can tell the diff.
because here on Earth, mass and weight both free fall
at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Erm...if one has a mass and one has a weight, then one has
two objects of indeterminate mass and weight.
Ponder that for a moment.
As it is, units of mass are different from units of weight,
although most laypeople confuse the two.
But then, the obvious conclusion is that most laypeople are idiots. :-)
Hey, Ghostie, I bet if you revealed yourself, we could find out who
the idiots are!
In other words, tell us what you think some units are--nail down your
position, not just some vague bitching.
By all means, have some units.
Mass: kg.
Weight: Newtons.
Length: meters
Pressure: Pascal (Newtons/m^2)
Time: seconds
Speed: m/s
Acceleration: m/s/s or m/s^2
Force: Newtons (same as weight).
A mass of 1 kg presses down on the hand with a force of 9.80665 Newtons,
more or less, on Earth. This "conversion" factor is quite variable
(it depends among other things on what planet one is on and how
high above the center one is), and a more reliable conversion was
initially attempted (AFAIK, mostly successfully; subsequent attempts
have improved the value) to find G in the formula
F = G * M * m/r^2
which is an idealization anyway (a better formula would use an
integral over the mass of the Earth) but works for simpler stuff.
G in this case is 6.6873 * 10^-11 m^3 / (kg * s^2). M is the
mass of the Earth, which is about 5.976 * 10^24 kg. d is the
radius of the Earth, which is 6.378*10^6 m. Plugging in
these values gives a g' of 9.824, so my units aren't all that
consistent.
I'll forbear angular measurements as I'm not all that familiar
with them beyond noting that radians is an important component
thereof. (1 radian is the angle subtending 1m of circumference
on a circle of radius 1m. It's just shy of 60 degrees.)
I'll bet you aren't any smarter than Shead and Uncle Al. What about
those troy pounds Uncle Al was talking about earlier this week in
another thread on sci.physics and alt.sport.hockey.nhl.det-redwings,
are they units of mass or units of force?
Mass.
Avoirdupois pound--mass or force?
Mass.
Short hundredweight--mass or force?
Mass, most likely.
U.S. fluid ounce--mass or force?
Neither; it's a unit of volume.
Kilogram--mass or force?
Mass.
Poundal--mass or force?
Force.
Hyl--mass or force?
I'd have to look. Google suggests 1 Hyl = 9.80665 kg.
Therefore, mass.
Slug--mass or force?
Mass.
Pennyweight--mass or force?
Most likely mass.
Slinch (1 lbf s²/in)-- mass or force?
That is one strange unit. Looks like it might be mass
(1 N = 1 kg * m / s / s; therefore 1 kg = 1 N * s * s / m)
but strangely expressed. (It came through as \262 on my
viewer, which didn't help; presumably that's '^2'.)
Good job, Ghost! I'll bet that Shead and his buddies misinterpreted
what you said in your earlier message, so I'm glad I got you nailed
down on this.
Now I'll sit back and wait for someone to try to prove you wrong.
Only thing that's still got me buffaloed is where you imagine that
"units of mass" are different from "units of weight," and "laypeople
confuse the two." I've seen much more confusion among engineers and
scientists and science teachers than in the general public.
Of course, the avoirdupois pound and the kilogram have also spawned
the pound force and the kilogram force. But the keepers of our
standards have been telling us for over 40 years to stop using
kilograms force. But the thing is, when we do still see kilograms
force used, it generally isn't by "laypeople" but rather in some
technical context.
Well, you've got that more or less right, except that it's not
quite general enough. Any two masses will exhibit a force.
Take two 50 kg masses (1 male, 1 female) and space them 1 m apart,
and the gravitational attraction will be about 1.67 * 10^-7 Newton,
or perhaps 1.67 * 10^-2 dynes might be a better method of expression.
Better?
So, you don't accept the authority of the BIPM and the NIST and every
other standards-setting agency to tell you to quit using dynes.
I use Newtons because it's part of SI. Dynes are part of cgi, an
older standard but still useful. Better in that the human mind relates
a little more easily to 0.0167 than 0.000000167, and in any event,
it's fairly small.
Do you object to the use of kilograms force? If so, please explain on
what authority you do so, if nobody has the authority to tell you to
quit using dynes.
If one has a precise definition of kg-f, then by all means use it.
I even have a conversion-factor: 1 kg-f = 9.80665 N.
Yes, we do have a precise definition of kilograms force.
But kilograms force are no more acceptable in the modern metric system
than microns or dynes.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
.
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| User: "The Ghost In The Machine" |
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| Title: Re: Mass versus Weight |
22 Apr 2004 11:00:21 AM |
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In sci.math, Gene Nygaard
<gnygaard@nccray.com>
wrote
on Mon, 19 Apr 2004 11:26:12 -0500
<bou780djcl1chtjge2iusu7darjdiudtqq@4ax.com>:
On Mon, 19 Apr 2004 16:00:22 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Gene Nygaard
<gnygaard@nccray.com>
wrote
on Sun, 18 Apr 2004 12:12:47 -0500
<dvc580tt1irv461r272lh4sg3bl1jhnkhq@4ax.com>:
On Sun, 18 Apr 2004 00:00:43 GMT, The Ghost In The Machine
<ewill@sirius.athghost7038suus.net> wrote:
In sci.math, Donald G. Shead
<dcshead@charter.net>
wrote
on 15 Apr 2004 06:00:14 -0700
<48402bae.0404150500.55bae6f5@posting.google.com>:
- Mass versus Weight -
UP we stand; DOWN we fall(;^) 4/4/'04
Mass and weight are easy to confuse,
For idiots, maybe. Most people can tell the diff.
because here on Earth, mass and weight both free fall
at the same rate [g/2 = s/t^2 = about
16'/sec^2]: Galileo discovered this empirically, by rolling objects
down inclined planes and carefully timing and observing them.
Erm...if one has a mass and one has a weight, then one has
two objects of indeterminate mass and weight.
Ponder that for a moment.
As it is, units of mass are different from units of weight,
although most laypeople confuse the two.
But then, the obvious conclusion is that most laypeople are idiots. :-)
Hey, Ghostie, I bet if you revealed yourself, we could find out who
the idiots are!
In other words, tell us what you think some units are--nail down your
position, not just some vague bitching.
By all means, have some units.
Mass: kg.
Weight: Newtons.
Length: meters
Pressure: Pascal (Newtons/m^2)
Time: seconds
Speed: m/s
Acceleration: m/s/s or m/s^2
Force: Newtons (same as weight).
A mass of 1 kg presses down on the hand with a force of 9.80665 Newtons,
more or less, on Earth. This "conversion" factor is quite variable
(it depends among other things on what planet one is on and how
high above the center one is), and a more reliable conversion was
initially attempted (AFAIK, mostly successfully; subsequent attempts
have improved the value) to find G in the formula
F = G * M * m/r^2
which is an idealization anyway (a better formula would use an
integral over the mass of the Earth) but works for simpler stuff.
G in this case is 6.6873 * 10^-11 m^3 / (kg * s^2). M is the
mass of the Earth, which is about 5.976 * 10^24 kg. d is the
radius of the Earth, which is 6.378*10^6 m. Plugging in
these values gives a g' of 9.824, so my units aren't all that
consistent.
I'll forbear angular measurements as I'm not all that familiar
with them beyond noting that radians is an important component
thereof. (1 radian is the angle subtending 1m of circumference
on a circle of radius 1m. It's just shy of 60 degrees.)
I'll bet you aren't any smarter than Shead and Uncle Al. What about
those troy pounds Uncle Al was talking about earlier this week in
another thread on sci.physics and alt.sport.hockey.nhl.det-redwings,
are they units of mass or units of force?
Mass.
Avoirdupois pound--mass or force?
Mass.
Short hundredweight--mass or force?
Mass, most likely.
U.S. fluid ounce--mass or force?
Neither; it's a unit of volume.
Kilogram--mass or force?
Mass.
Poundal--mass or force?
Force.
Hyl--mass or force?
I'd have to look. Google suggests 1 Hyl = 9.80665 kg.
Therefore, mass.
Slug--mass or force?
Mass.
Pennyweight--mass or force?
Most likely mass.
Slinch (1 lbf s²/in)-- mass or force?
That is one strange unit. Looks like it might be mass
(1 N = 1 kg * m / s / s; therefore 1 kg = 1 N * s * s / m)
but strangely expressed. (It came through as \262 on my
viewer, which didn't help; presumably that's '^2'.)
Good job, Ghost! I'll bet that Shead and his buddies misinterpreted
what you said in your earlier message, so I'm glad I got you nailed
down on this.
Now I'll sit back and wait for someone to try to prove you wrong.
That won't take long. MKS is neither right nor wrong, merely useful.
Only thing that's still got me buffaloed is where you imagine that
"units of mass" are different from "units of weight," and "laypeople
confuse the two." I've seen much more confusion among engineers and
scientists and science teachers than in the general public.
Of course, the avoirdupois pound and the kilogram have also spawned
the pound force and the kilogram force. But the keepers of our
standards have been telling us for over 40 years to stop using
kilograms force. But the thing is, when we do still see kilograms
force used, it generally isn't by "laypeople" but rather in some
technical context.
kg-f is useful for, say, modeling the problem of a support pillar.
I'll admit I'd probably use Newtons but it may depend on one's training.
Well, you've got that more or less right, except that it's not
quite general enough. Any two masses will exhibit a force.
Take two 50 kg masses (1 male, 1 female) and space them 1 m apart,
and the gravitational attraction will be about 1.67 * 10^-7 Newton,
or perhaps 1.67 * 10^-2 dynes might be a better method of expression.
Better?
So, you don't accept the authority of the BIPM and the NIST and every
other standards-setting agency to tell you to quit using dynes.
I use Newtons because it's part of SI. Dynes are part of cgi, an
older standard but still useful. Better in that the human mind relates
a little more easily to 0.0167 than 0.000000167, and in any event,
it's fairly small.
Do you object to the use of kilograms force? If so, please explain on
what authority you do so, if nobody has the authority to tell you to
quit using dynes.
If one has a precise definition of kg-f, then by all means use it.
I even have a conversion-factor: 1 kg-f = 9.80665 N.
Yes, we do have a precise definition of kilograms force.
But kilograms force are no more acceptable in the modern metric system
than microns or dynes.
If they're useful, perhaps they should be?
As it is, I see Newtons being more straightforward.
Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/
--
#191,
It's still legal to go .sigless.
.
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