English vs Metric Units: Pros and Cons

[Bryan Parry]

Originally posted by russ_watters
Actually, you've already answered most of your own questions and the rest have been answered by others. To put it all together though: I'm an engineer and I deal with practical things, not theoretical ones. I use a system of measurement which makes sense for me and my particular application.

No, I am not clear on the exact nature of the relationship between pound-f, pound-m, slug, and poundal. And that's the problem in a nutshell: its unnecessarily complicated. 4 different weight/mass units? In the SI system, there is force and there is mass. Force is force and mass is mass. Simple.
These days, it seems we are using a hybrid system in the US: I first learned english-si conversions in elementary school when I learned a "pound" is 2.2kg. Pound-f? Pound-m? No, just a "pound." And that's what I use today.

Force and mass are virtually interchangeable: How much does a 150lb man weigh on the moon? 150lb of course! Or did you think I meant he's 150lb on Earth in which case you are using pounds-f as a mass and need to divide by 6? All of my dry food containers say ounces and grams. That's: ounce-force-mass.

We use weight and mass interchangeably in almost every situation where weight, mass, or density is an issue (the density of water is 1g/cc or 62.4lb/sq ft). Is "pound" a force or a mass in this context? I don't care!

In aerospace courses, I was introduced to the slug and still occasionally use it, but not often. In my every day life, I use si if I need an f=ma calculation, because its simpler and less confusing than converting pounds to slugs before putting it into the equation.

So why is the English system bad? Simple and already answered: its counterintuitive and unnecessarily complicated. I'd be quite happy to do away with it. Comodities are priced in ounces. A bar of gold weighs (weighs?!) about 50 pounds. How tall are you? Inches? Feet-inches? Not in the US, you won't. Not to worry: you'll never find a "loo" or a "telly" either. I don't know if this is because of the "loo" and "telly" issue, but that's not how it works in the US. Laymen use pounds as pounds and don't differentiate between mass and weight (force). I just drank 12 ounces of soda (uh oh - they're fluid-ounces, not ounces-ounces - wth is a fluid ounce?). Pounds are a force, mass, or weight depending on what the situation requires (when I'm doing a bench press, am I lifing a mass or a weight, or just applying a force?) Kg are always mass and I've never heard of a kg-f (is there also a Newton-mass?).

As someone in another thread brought up and I pointed out, the SI system isn't perfect in its usage either: a bathroom scale that tells you you weigh 90kg is using weight and mass interchangeably. Maybe in England, but not in the US. Thats another manifestation of the problem caused by all the ambiguity. Here's the american dictionary def of pound: http://dictionary.reference.com/search?q=pound

Abbr. lb.
A unit of weight equal to 16 ounces (453.592 grams).
A unit of apothecary weight equal to 12 ounces (373.242 grams). See table at measurement.
A unit of weight differing in various countries and times.
A British unit of force equal to the weight of a standard one-pound mass where the local acceleration of gravity is 9.817 meters (32.174 feet) per second per second.

With respect, Russ, I more-or-less disagree with everything you have just said.

For a start, you say we have two mass units in English and two of force (slug and pound, pound-force and poundal). This is ***THE SAME** in metric. You have the gravitational system that consists of the TME & Kilogramme-force, and the normal system with the Kilogramme and Newton. Likewise, with English we have one system that is gravitational (slug and pound-force), and another that is not (pound and poundal).
With respect, and I really hope I don't sound rude here as it is meant not in that way at all, but if you are an Engineer in the States who does not understand the relationship 'tween slug, pound, pound-force, poundal, then I am not entirely sure how you became an engineer. This relationship is so basic you really ought to know it (European engineers know the difference 'tween TME, kilogramme, kilogramme-force, Newton, and all American engineers that Italk to understand slug-pound-poundforce.
It is true that Americans don't generally use the poundal for some reason, but do use the pound as it is primarily a mass unit, which results in a minor anomaly, but that is scarcely the fault of the english system, but rather the fault of the standards agencies, the US government, and perhaps the US educational system.

Russ, in another part of your message you are misleading. You talk of how much a 150lb man 'weighs'- you and I both knwo that that is an extremely ambiguous word. "Weight" usually refers to mass, but can do force as well. You would do better to say how much is his force or mass to clarify this ambiguity. This problem, as it is, arises in metric as well, as nobody uses the Newton to weigh themselves, but the kilogramme-force. Why? Because for most people mass and force are the same, in effect, and there is no need to distinguish. Also, most people do not want to do the conversions (1kgf = 9.81N, or 1lb = 32.2pdl), as most everything they use has its mass measured (e.g. a lb of bananas)

I would disagree on your ascertion that English is counter-intuitive. But such arguements are so esoteric I will not try to have you on this point.


I will say that, as you say, most people do not distinguish between pounds and pound-force (just like most people do not distinguish between kilogrames and kilogrammes-force- if you think the Newton is ever used for "common" things in Europe, you are seriously mistaken).
As for {fluid) ounces versus ounces, this seems a US issue. In Britai nwe talk of fluid ounces and ounces, and not ounces and ounces. Regardless, in the everyday world, it is obvious which you mean based on context. For instance, if you say "pass us that 12-oz tin of coke", it is obvious you mean 12floz, but if you said, "this recipe requires 12 ounces of beef", that too makes it clear wher you mean the mass unit or the capacity unit.
What is a "fluid" ounce. Well, the name is a little historical, but you know it means "volumetric ounce" (of water in UK, of Wwine in USA)

As for that definition of the Pound, I will say this: of course it varied throughout history. Now it does not. The apothecaries and troy pound is never used; they have been unused and 'obsolete' for a long time.
The ambiguity 'tween pounds of mass and force I have already got into a bit.


Cheers :)

 

[Michael D. Sewell]

During this discussion I have found value in each of the systems; for that, I thank you all.
-Mike

 

[Integral]

Originally posted by Michael D. Sewell
Integral-You are wrong. The correct dimensions of a dressed 2 x 4 are 1 1/2" x 3 1/2". I have handled thousands upon thousands of both rough and finished 2 x 4s in my life. I remember when we made the change from the dimensions you listed. Precut studs cost $.68 each at the time. We were building houses for about $17,000.00 The old surveys for the properties often gave the traverse lengths in links and chains. 10 square chains make an acre, and 80 chains make a mile. Simple enough, even for me. I think the english system has a lot of charm. -Mike

Guess my age is showing. Just stepped into my garage and measured a 2x4, by golly you are right. I surely have known that, because I have handled a few myself over the years. Its amazing what gets stuck in your head.

 

[russ_watters]

Originally posted by Bryan Parry
With respect, Russ, I more-or-less disagree with everything you have just said.

For a start, you say we have two mass units in English and two of force (slug and pound, pound-force and poundal). This is ***THE SAME** in metric. You have the gravitational system that consists of the TME & Kilogramme-force, and the normal system with the Kilogramme and Newton. Likewise, with English we have one system that is gravitational (slug and pound-force), and another that is not (pound and poundal).

Maybe I shouldn't bring this back, but this part seems to be the main sticking point. HERE is a website I often use. It lists the SI units as:

-------------------------------------------
Length metre m
Mass kilogram kg
Time second s
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd
-------------------------------------------

Judging by the responses of others, I'm not the only one who uses only these units for SI (except Newtons: strange it isn't listed, but I guess its not fundamental, but a derivation from f=ma). I quite frankly don't see the point of a kg-f, and have never heard of it before this thread - meaning though it exists, its not commonly used and may be obsolete, just like all those English units that have been recently discarded.

Units and measurement systems exist to be used. In actual use SI/metric is far simpler than the English system. Yes, that's an opinion, but its an opinion clearly shared by a lot of people. And the way I use these units I learned in two different, respectable American universities.

Quite frankly, I think your membership in the "Dozenal Society" gives you a very different perspective on units than the vast majority of other people haave.

I would be interested in learning more about these units though. Can you give me some examples of where, why, or how people would use a kg-f or a poundal?

edit: I found THIS on Wikkopedia:

In the relationship


F = m×a,
which is derived from Newton’s second law of motion, F is the force in Newtons, m the mass in kilograms and a the acceleration in meters per second squared. To a physicist, the kilogram is a unit of mass, but in common usage "kilogram" is a shorthand for "the weight of a one kilogram mass at sea level on earth". At sea level on earth, the acceleration due to gravity (a in the above equation) is 9.807 meters per second squared, so the weight of one kilogram is 1 kg × 9.807 m/s² = 9.807 N.

To distinguish these two meanings of "kilogram", the abbreviations "kgm" for kilogram mass (i.e. 1 kg) and "kgf" for kilogram force, also called kilopond (kp), equal to 9.807 N, are sometimes used. These are only informal terms and are not recognized in the SI system of units.

 

[Bryan Parry]

Originally posted by russ_watters
Maybe I shouldn't bring this back, but this part seems to be the main sticking point. HERE is a website I often use. It lists the SI units as:

-------------------------------------------
Length metre m
Mass kilogram kg
Time second s
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd
-------------------------------------------

Judging by the responses of others, I'm not the only one who uses only these units for SI (except Newtons: strange it isn't listed, but I guess its not fundamental, but a derivation from f=ma). I quite frankly don't see the point of a kg-f, and have never heard of it before this thread - meaning though it exists, its not commonly used and may be obsolete, just like all those English units that have been recently discarded.

Units and measurement systems exist to be used. In actual use SI/metric is far simpler than the English system. Yes, that's an opinion, but its an opinion clearly shared by a lot of people. And the way I use these units I learned in two different, respectable American universities.

Quite frankly, I think your membership in the "Dozenal Society" gives you a very different perspective on units than the vast majority of other people haave.

I would be interested in learning more about these units though. Can you give me some examples of where, why, or how people would use a kg-f or a poundal?

edit: I found THIS on Wikkopedia:

Just for the record (English system):

Length Foot ft
Mass Pound lb
Time second s
Electric current --No units (other than metrical ones)--
Temperature Rankine R
Amount of substance Poundmole lbmol
Luminous intensity candle




Anyway, on to your message...

As far as I am concerned, 'obsolete', just like 'arbitrary', is a word that seem to be bandied about in these kind of debates without any real thought. I would say that, as in many engineering fields, the kilogramme-force and the pound-force are preferred over the Newton and poundal. This results in often being required to use the TMe/hyl and slug.
The problem essentially arises as there is an awkward relationship between thebasic units both in metrical systems and English ones (i.e. the acceleration of gravity is not great). Thus, we end up with the above situation.
I would say that the Newton and kilogramme ARE more often used than the english equivalent of Pound and poundal, but that is merely because English does not have the vast network of officaldom's support behind as SI does. It is because of this that the slug-pound-poundforce situation is more of an "issue" when using english units than when using metric SI; people simply use what is most practical (given issues raised by g's figure in these systems of ours) without being given advice on which units are 'preffered' as is the case in SI.
Back on to 'obsolete', though- I would say that units still used and serving a purpose, are far from 'obsolete'. I certainly shouldn't like to tell all of those english and metric engineers that their units, and probably they themselves, are 'obsolete'.



As for my membership of the dozenal association, I shall clarify. Dozenalists are a diverse bunch- like any group of people. Some dozenalists believe the only way forward is to adopt a base-12 counting system and have a system of weights and measures where the units are related totally by the factor 12 and its squares, cubes etc. However, some other dozenalists just believe that the number 12 should play a large part in present systems of W&M within the context of a base-10 numeral system. I am more the latter than the former.

Bearing this acceptance of mine of the base-10 counting system that we all use, and also keeping in mind the issues (touched on above) relating to g as a troublesome pseudo-constant, I have devised some alternative systems of W&M.
Given we are working within a base-10 counting system, the factors of much use are 10, 100, 1000 etc, and 2 and 5. Thus I bring you to the core of three alternative systems- one metric-slanted (in a way), and two English slanted.



Inch-Pound_Trice
This system was designed by Andrew Usher and Leonard Cottrell. I shall link you to a page on the units system.

IPT

Foot-Pound-Quarter
By use of a unit of time- I call the 'quarter [second]'- equal to EXACTLY 0.25 seconds, we have reduced g to 2.010878 feet per quarter squared. Far more manageable and useful than the English 32.17405ft/s/s or the SI 9.80665m/s/s

The corresponding force unit is equal to 0.497 pounds of force. This unit is called the mark (from the many 8oz / half-pound units historically widespread on the European continent and in Britain)

Alen-Mark-Quarter: a variant system
This systems introduces a metric-style equivelance 'tween mass, capacity and volume units (1 CC = 1ml = 1g)
This is due to make a length of EXACTLY 2ft become the length unit (the alen: from the 24" units of europe of this name, related to the 'ell'). The mass of a volume of 1 cubic alen of water is now equal to 500 pounds.. or 1000 marks (hence the change in mass unit)
Obviously, due to a length unit equal to exactly 2 ft, g is now effectively taken out of the equation, with g accelerating at 1.005439alens per quarter squared (at 45 degrees sea level)

****** The advantage of both of these systems is that they fix some fundamental and frankly embarressing problems with English- one of which is shared with metric- and are completely usable i nthe context of a nation using the Traditional English units (due to exact conversion between marks and pounds, alens and feet, quarters and seconds (2:1, 1:2, 4:1 respectively)

New Metric- based on the decimal time system
The reason the metre is its length is due to it being based on a fraction of the Earth's ciorcumference by way of the centesimal system of angular measurement (1 right angle = 100 grads)
This system was shortly abandoned (along with the corresponding decimal time), and so thus the metre became irrelevant.
However, this system looks as if it may make a return after being repackaged by swatch as "internet time", with 1 "metric second"- the "blink"- being equal to 0.864 secs (1/100,000 days).
In such a system g = 288.2"

My variant comes from the view that the Earth's circumference is no longer relevant (and never really was), so that making g = a sensible number (either 1, 10, 100, 1000... or 2) is of primary importance. I say that g is 10 "metres" per "blink" squared.

This results in the following:

New Metre (I call it 'arshin')= 28.82"
New Kilogramme (I call it 'funte')= 13.84oz
New Newton (I call it 'tael')= 1.384ozf

[the names are fro mthe Russian and East Asians units of similar sizes]




Cheers, I hope this has been of interest.

 

[Bryan Parry]

Whoops!

Just realized I never responded to the following point of yours, Russ:


>>>>>>>>>>>>>>>>>>>>>>>>>>
quote: Bryan Parry
--------------------------------------------------------------------------------
Much of it is pure nonsesne, anyway. Like, for instance, how many pounds in 200 ounces- when in the hell would you continue measuring in ounces beyond two ro three pounds? Complete and utter rubbish.
--------------------------------------------------------------------------------

Russ:
Comodities are priced in ounces. A bar of gold weighs (weighs?!) about 50 pounds.
<<<<<<<<<<<<<<<<<<<<<<<<<<<



Russ, gold is priced in troy ounces (God knows why not avoirdupois- probably because, setting aside historical reasons, the smallest subdivision in the troy system is 1/480 try ounces, whereas in avoird, it is 1/16oz (the grain is not effectively part of avoird.)), and the troy pound was abolished i nthe nineteenth century.. so if gold is still priced in troy, then it can ONLY be priced in ounces, regardless of how many pounds weight of gold you have! Actually, if the troy pound had not been abolished, you almost certainly would see gold etc dealt with by the pound-troy instead, and not so many hundred ounces.

Other items are priced in ounces, though, as I said, up to a point, and then it naturally shifts to the pound.