Science > Physics > Express quantities of force and mass in weight units; not inertia units:
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Science > Physics |
| User: |
"Don1" |
| Date: |
07 Oct 2005 08:58:29 PM |
| Object: |
Express quantities of force and mass in weight units; not inertia units: |
It's easier to express quantities of force and mass in units of weight
(w), than in units of inertia (w/g); then you'll know how heavy they
are right off the bat.
Don
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| User: "snapdragon31" |
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| Title: Re: Express quantities of force and mass in weight units; not inertia units: |
08 Oct 2005 01:12:39 AM |
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Don1 wrote:
It's easier to express quantities of force and mass in units of weight
(w), than in units of inertia (w/g); then you'll know how heavy they
are right off the bat.
Don
Not really. In real life, people use mass rather than force to
represent weight. For example, my cat's weight is 2 kg (in SI unit) or
4.4 lb (British unit). lb and kg are mass unit (i.e. m or w/g).
The correct way to express weight should be in kgf (kilogram force), N
(Newton), lbf (pound-force), pdl (poundal) ... etc
In the supermarket, the fruit and vegetable are usually sold at $/kg or
$/lb not $/kgf or $/lbf.
It is normal to say 1 kilogram of apple or 1 pound of orange.
No body would say 9.8 Newtons of apple or 32 poundal of orange in real
life.
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| User: "Don1" |
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| Title: Re: Express quantities of force and mass in weight units; not inertia units: |
08 Oct 2005 07:38:49 AM |
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snapdragon31 wrote:
Don1 wrote:
It's easier to express quantities of force and mass in units of weight
(w), than in units of inertia (w/g); then you'll know how heavy they
are right off the bat.
Don
Not really. In real life, people use mass rather than force to
represent weight. For example, my cat's weight is 2 kg (in SI unit) or
4.4 lb (British unit). lb and kg are mass unit (i.e. m or w/g).
The correct way to express weight should be in kgf (kilogram force), N
(Newton), lbf (pound-force), pdl (poundal) ... etc
In the supermarket, the fruit and vegetable are usually sold at $/kg or
$/lb not $/kgf or $/lbf.
It is normal to say 1 kilogram of apple or 1 pound of orange.
No body would say 9.8 Newtons of apple or 32 poundal of orange in real
life.
Of course not the only right way to express weight; which is a force,
is in _pounds of force_. The metric system screwed us up royally, and
is still doing it; with their standard kilogram of inertia.
The newton (N) is not a good unit for expressing force, because it's
too darn small.
Metricists haven't figured out yet the difference between weight and
mass; that mass divided by the acceleration due to gravity is force.
Confusion will reign, until we come to our senses and realize that
inertia is a measure of the mass that makes up bodies of matter, and
that mass, and inertia are expressed as a ratio of force (f), divided
by the rate of displacement (s/t^2) that it causes; which may be more
concisely expressed as ft^2/s, and is equal to a body's weight (w)
divided by the acceleration (g) at which it will free fall.
The customary system of weights and measures was never in dispute; it's
working as good now as ever.
Don
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| User: "The Ghost In The Machine" |
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| Title: Re: Express quantities of force and mass in weight units; not inertia units: |
08 Oct 2005 01:00:07 PM |
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In sci.math, Don1
<dcshead@charter.net>
wrote
on 8 Oct 2005 05:38:49 -0700
<1128775129.209598.23640@g44g2000cwa.googlegroups.com>:
snapdragon31 wrote:
Don1 wrote:
It's easier to express quantities of force and mass in units of weight
(w), than in units of inertia (w/g); then you'll know how heavy they
are right off the bat.
Don
Not really. In real life, people use mass rather than force to
represent weight. For example, my cat's weight is 2 kg (in SI unit) or
4.4 lb (British unit). lb and kg are mass unit (i.e. m or w/g).
The correct way to express weight should be in kgf (kilogram force), N
(Newton), lbf (pound-force), pdl (poundal) ... etc
In the supermarket, the fruit and vegetable are usually sold at $/kg or
$/lb not $/kgf or $/lbf.
It is normal to say 1 kilogram of apple or 1 pound of orange.
No body would say 9.8 Newtons of apple or 32 poundal of orange in real
life.
Of course not the only right way to express weight; which is a force,
is in _pounds of force_. The metric system screwed us up royally, and
is still doing it; with their standard kilogram of inertia.
Mass, you mean. Weight=force is fine, of course, but you'll never
get it.
The newton (N) is not a good unit for expressing force, because it's
too darn small.
So use a meganewton instead. Duh, that was easy.
1 atm = 101.325 kPa, for another example. The threshold of
hearing at 1 kHz is 1 picoWatt/m^2, so we wouldn't want *too*
big a unit of force; we wouldn't be able to hear you. :-P
It could be worse. Prior to SI, we had cgs, which among other
things had a dyne as the standard unit of force. The amount
of force 1 gram exerts on the hand can be expressed as 980.5 dynes,
give or take, and 1 dyne is 10^-5 Newton.
Metricists haven't figured out yet the difference between weight and
mass; that mass divided by the acceleration due to gravity is force.
You mean *YOU* haven't figured it out yet. Both SI and cgs had
it figured out long ago. Why do you think we have Newtons and
kg, or dynes and grams, or even for that matter poundals and pounds,
or pounds-force and slugs?
Different things, different units, unfortunately same old Donald.
[rest snipped]
--
#191,
It's still legal to go .sigless.
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| User: "Bob Cain" |
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| Title: Re: Express quantities of force and mass in weight units; not inertia |
08 Oct 2005 04:24:19 AM |
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Don1 wrote:
It's easier to express quantities of force and mass in units of weight
(w), than in units of inertia (w/g); then you'll know how heavy they
are right off the bat.
There's no such thing as weight. Some fool nouned a verb
somewhere along the way and it stuck.
Bob
--
"Things should be described as simply as possible, but no
simpler."
A. Einstein
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| User: "" |
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| Title: Re: Express quantities of force and mass in weight units; not inertia units: |
07 Oct 2005 09:08:32 PM |
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I'll consider that, but there's pecans to harvest first.
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