The metric system of units is best !!!

[bertyboy]

The old imperial system of units which we British discarded in favour of the SI ( metric ) system of units, was a total joke. In hindsight I can believe that we British invented such a stupid system, it could only have happened in Britain !. If someone was simple, and completely drunk, they couldn't come up with a more stupid system.
However I can't believe that you Americans are still using it !
I am old enough to have experienced both systems during my life, as we in Britain changed over to the metric system gradually from 1970 on, this change started with the change of our money, called decimalisation.
The last remnants of the old system are still being eroded away today, as we still measure petrol in gallons, beer in pints, and buy meat in pounds. But I suspect in another 10 years it will completely disappear. Although miles may never disappear !
Have there been any suggetions or moves within the US, to drop the ridiculous Imperial system and replace it, with the sensible, and logical metric system. A system that most of the world has been smart enough to have adopted ?

 

[EnglishMuffin]

Corus : that's a good one - sorry I misspelled "Napoleon" -just a typo. He did found the Ecole Polytechnique, I suppose, which gave us the bulk of the theory of elasticity. But then again, he himself wasn't actually French!

bertyboy : And what, pray, was so smart about defining the metre as one ten-millionth of the distance from the equator to the North Pole along a meridian passing close to Paris (where else)? Nobody could agree on what the distance was, so they ended up having to use a length standard very similar to the imperial master yard!

 

[EnglishMuffin]

Actually, having quoted all this stuff about Napoleon from memory, I decided to look up some web sites and found this one, which seems to contradict some of the things I said :

http://www.arvonia.net/~anti-metrics/fixed/USMA01/fixed.html

And on this site, they give a quote of Napoleon's :

"The scientists adopted the decimal system on the basis of the metre as unit. Nothing is more contrary to the organization of the mind, memory and imagination. The new system will be a stumbling block and source of difficulties for generations to come. It is just tormenting the people with trivia." - Napoleon Bonaparte

Nothing changes, does it ?

 

[hernma]

We have to differentiate the SI system from the metric or thecnical system. I agree complete in using the metric system, it is simple and easy to use, as many of you have pointed out. The SI system is not so simple and is not popular in Latin America, even this countries have adopted it officially.

Just to organize my point: the SI uses a scientific concept: weight = mass x gravity, so Kg (force or weight) = Kg (mass) x 9.81 m/s2 = 9.81 N … therefore all the chain of the 10´s is lost, and to assimilate to “old units” we take Kg(f) = +/- 10 N.

¡ All a confusion to be understood for people that are not engineers!

There is a relation: 1 litre of water weights 1 Kg, and 1 m3 = 1 T, which we lost with the N.

Imagine, a dependant asking in a supermarket, how many kN of meat a person wants! . .. I feel it is going to be very difficult that comun people assimilates and change Kg for Newtons, and how EnglishMuffin suggests,... aren´t we in the middle of a contest?

Normally, we make all the calculations and designs in metric, and if necessary, write down afterwards in SI.

A similar discussion took place in thread 507-59926, “KIPS”.

 

[IRstuff]

Unless you are running differing amounts of gravity in different stores, there is no need to use any other unit than a kilogram. The kilogram is the SI unit. SI is the metric system. In fact, if you look at:

http://physics.nist.gov/cuu/Units/units.html

you can see that the accepted SI units DO NOT include Newtons, since that's dependent on g, which is not a constant. The Newton is a derived unit, since it is technically a composite of 3 basic SI units.

Even our illegal drugs are bought in kilos;-)

TTFN

 

[Ingenuity]

And in the USA even legal drugs and medicine are sold and administered in "cc", mL, mg. But the doctors/nurses still determine body mass in lb's...maybe they measure in kg then convert to lb because most US patients do not know what a kg is!

 

[DanTex]

Most women I know would just LOVE to convert to kilograms if someone would explain to them that their body weight "values" would be cut in half.

Dan

 

[EnglishMuffin]

hernma: why would you want to price and/or buy meat in Newtons ? I suppose that would be an advantage for some future Moon dweller, since they would get about six times as much for their money.

IRstuff : What on earth are you talking about? The Newton unit has nothing whatsoever to do with the value of "g", and as far as I am aware was introduced specifically for the SI system in the mid 20th century.

 

[IRstuff]

Sorry, must have been the illegal drugs ;-) throwing me off.

should have been something like:

you can see that the accepted SI units DO NOT include Newtons. The Newton is a derived unit, since it is technically a composite of 3 basic SI units.

I'm not even sure where I was going with the g's comment.

TTFN

 

[EnglishMuffin]

Saaright! You know, I'm beginning to think that Napoleon was "right on" in that quote about 7 posts back! Before the French Revolution, the French system was even more confusing than the British system - virtually every major town had its own standards. But the new system got them even more confused, and Napoleon had to rescind it in 1812. It wasn't reinstated until about 1840.

 

[hernma]

I was in Canada once , but as a tourist, so I didn’t have the opportunity of buying anything by weight, and I would be aware of the exception , definition or synonymous given in “SI unit rules and style conventions”: “# 19: WEIGHT vs. MASS When the word “weight” is used, the intended meaning is clear. (In science and technology, weight is a force, for which the SI units is the newton; in commerce and everyday use, weight is usually a synonym, for mass, for which the SI unit is the kilogram.)”

So, I understand why my quotation of buying the meat in kN was hilarious to you; to me, what probes is only that my wife has reason when she says that every once I go for shopping to the supermarket, all becomes a mess.

What… for the rest, my point remains: SI for commerce introduces a synonym for mass and weight (since the kg is a base unit of mass ---- ¿ doesn’t sound a little forced to you?).

But let’s talk about engineering: weight / area is pressure, which in what I call metric system (with your permission IRstuff), weight is measured in T and area in m2, so very simple and direct (as in US units), pressure = T/m2.

According to the reference given by IRstuff ( a very good one), in “Units outside the SI that are accepted for use with the SI”, it is accepted the metric ton = 1000 kg. So that, in the case of pressure, the weight will be measured in T, the area in m2 , but the results have to be expressed Pa, MPa or N/m2.

I could go on and on and on, but it doesn’t worth, the idea is clear and as said, my point remains : what the newton was invented for?

 

[IRstuff]

For convenience.

The same is true of the joule, which is kg-m^2/s^2 or watts, which is kg-m^2/s^3. There is little intuitive recognition using the base units, unless you're one of those that can readily parse multiple units and powers in real time.

Whereas, on the hand, a joule is immediately recognizable as a unit of energy and watt as a unit of power. It's a shorthand, in the same vein as kilo, giga, etc. The derived units allows one to conveniently express complex quantities simply, with having to resort to expressing a very commonly used unit as:

kg-m^2/s^3-A

Isn't volt much simpler and easier to understand and use?
As for the meat, that's a custom, more than anything to do with the units. A kilo of beef is a piece of meat with a mass of 1 kilogram. There's no need to involve anything to do with weight, except as a means of figuring out the mass.

TTFN

 

[flamby]

IRstuff,

My understanding is
jule = N . m
watt = N. m/sec
N = m(mass) *g (graviational const)

If we follow this, the gravitational acceleration 'g' is inherent in the units you mention. But I am perplexed, that this comes from you.

You are Aero guy, so not hard for you to say that work done in far out space is much less than what we do here in our offices where g is high, and sometimes nerve breaking!

 

[IRstuff]

Definition of newton is:
N=kg*m/s^2,

see same NIST link referenced above, about 1/2 way down the page.

Newton is the unit of force=mass*acc, NOT mass*g.

Joule is the unit of work=f*dist=kg*m^2/s^2=N*m
Watt is a the unit of power=J/s=kg*m^2/s^3=N*m/s

BUT, the point is that the newton is NOT a fundamental unit, it's a derived unit, conposed of other fundamental units.

Likewise joules, watts and volts are derived units.

So if we were to use only "metric" units, we would be restricted from using newtons, joules, watts, volts, etc, since they are not fundamental metric units.

TTFN

 

[flamby]

Thanks IRstuff for brushing off the confusion!

 

[BigH]

For those interested - this has been discussed, too, in a thread with "KIP" in its title. If I start a job in Imperial - I like to stay with it; if it is started in SI (not metric), I can stay with it. It is a 'itch if you have to switch over in middle of job (i.e., at Syncrude tar sand mining in 1970s). SI is okay but I find that, still, engineers can't agree on a common unit - I like kPa or MPa; others go for N/mm2; still others tonnes/m2. I know it is typically factors of 10 - maybe even the same, but, let's pick kPa and stick with it for all pressures, eh?

Best to all - I'll be reading the thread again. It is good to see all the different views - global views at that.

 

[anka]

The metric system makes perfect sense when you grow up with it.
In everyday life, you order a "half" (half litre) in the pub, you set the airconditioning to 23 or 24, you buy one kg of beef, etc.
We calculate everything with ton and m.

Calculating in SI is a little tricky. We are not used to using MPa and mm yet, but are slowly making the conversion. We always convert 1kg=10N. Nobody uses 1kg=9.8N.

 

[EnglishMuffin]

You mean 1kgf=10N (approximately). 1 kg = 1 N*s^2/m, as IRstuff correctly stated.
Trouble is, the kgf (or kilopond) is not an SI unit. This thread must have confused the hell out of people that don't know anything about SI units.

 

[IRstuff]

Obviously, we're not learning from our mistakes. Bad enough to have lbf, but we now have to contend with kgf?

Yecch...

The moral of the story is that convenience dictates the creation of new words and new units, which will simply mean that metric will get more and more non-metric baggage over time.

TTFN

 

[BigH]

Why don't we just throw away the metric system and imperial and base all our computations on the "weight" and "volume" of a yard of ale!!! [fumanchu]

 

[DanTex]

Let's go have some ale and discuss the matter further!!!!

Dan

http://www.dtware.com