Hello Peter
> Just so you know "a couple of pick up loads" will be tons of the
> stuff. A small pick-up truck (like a Ford Ranger) is rated to hold about
> a 1,000 lbs (453.6 kg) to 1,500 lbs (680.4 kg) of mass (depending on
> suspension packages, it can hold maybe 25% more before it breaks, but
> that isn't a good thing to try). An Imperial Ton is 2,000 lbs[snip]
Oh no its isn't!
An imperial ton is 2240 lbs, not 2000 !
remember your school rules :-
16 oz = 1 lb
14 lb = 1 st
2 st = 1 qtr = 28 lbs
4 qtr = 1 cwt = 112 lbs
20 cwt = 1 ton i.e. 14 x 2 x 4 x 20 = 2240 lbs
If your math is right Dave, this is a beautiful illustration of the dangers of conventional wisdom. I asked 4 different guys today how many pounds in a ton and they all said:2000. I always thought it was
2000. If you're right on this,I'm gonna have to re-think my membership in the Flat Earth Society. I'll be phoning a scrapyard in the morning
1 short ton = 2000 lb
1 long ton = 2240 lb
1 metric ton = 1000 kg = 2205 lb-m
If you just say "ton," it might be interpreted as any of these, depending on the industry, application, and locale, so you should specify which you're talking about just to be sure, especially if money is involved! In case you're wondering, the first two are, technically speaking, units of weight, while the latter is a unit of mass; hence the use of "lb-m". One pound-mass (lb-m) will weigh one pound when acted on by the standard gravity of earth.
First of all, consider the troy "units of weight." Unlike their avoirdupois cousins, and unlike grams and kilograms and the like, these are always units of mass, never units of force. There is not and never has been a troy ounce force or a troy pound force. 1 oz t =
31.1034768 g exactly
The problem is that you are too poorly educated to understand the simple linguistic fact that "weight" is an ambiguous word, one with more than one meaning.
Second, the metric ton force is used, just as the gram force and kilogram force. These force units were endorsed and officially defined by the CGPM way back in 1901. They are not a part of nor acceptable for use with the modern version of the metric system, the International System of Units which was adopted in 1960--but we still see many vestiges of their use.
Occasionally you see "lbm" or some such symbol used to identify a pound mass, though that isn't sufficient to identify which pound mass (though lbm is as far as I have seen only used for the avoirdupois pound and never for the troy pound). However, it is the pound force, as the recent spinoff from the original avoirdupois pound which has been a unit of mass as long as it has existed, which ought to be identified as such and use the symbol "lbf" to distinguish itself from the "lb" for the older pounds as units of mass:
American Society for Testing and Materials, Standard for Metric Practice, E 380-79, ASTM 1979:
3.4.1.4 The use of the same name for units of force and mass causes confusion. When the non-SI units are used, a distinction should be made between force and mass, for example, lbf to denote force in gravimetric engineering units and lb for mass.
This sensible rule is followed by experts in this field, e.g. the national standards laboratories of the United States (NIST) and the United Kingdom (NPL).
Pounds force are such a recent invention that they are uniquely identified by that name. None of the hundreds of other pounds used in various times and places throughout history ever gave rise to a force unit of the same name that saw any significant use.
Third, long tons are used as units of force as well as units of mass in the United Kingdom. But in the United States and Canada, as far as I've seen, they are always used as units of mass.
These are the exact values:
1 short ton = 2000 lb = 907.18474 kg 1 long ton = 2240 lb = 1016.0469088 kg 1 metric ton = 1000 kg
Now the pound force doesn't even have an offical definition. This recent spinoff was never a well defined unit before some time around the turn of the 20th century, and no standard acceleration of free fall has been officially adopted for this purpose, as it was in 1901 for grams force. However, the value which is official for defining kilograms force (9.80665 m/s² exactly) is often borrowed for this purpose, though other values such as 32.16 ft/s² are also used for this purpose. Using that definition of the pound force which gives it the same relationship to a kilogram force as a pound has to a kilogram (something that doesn't necessarily have to hold true), we have
1 short ton force = 2000 lbf = 8.896443230521 kilonewtons exactly 1 long ton force = 2240 lbf = 9.96401641818352 kN exactly 1 metric ton force = 1000 kgf = 9.80665 kN exactly
with the same relationships between these short and long tons force and the kilogram force as we have above for these tons and kilograms. Using the 32.16 ft/s² standard acceleration of gravity, we'd have these rounded off values
1 short ton force = 906.78862 kgf = 8.89255867 kilonewtons 1 long ton force = 1015.6033 kgf = 9.9596657 kN
The problem is, Kurt, you asked 4 Canadians, and Dave is in the UK (based on a "bt..." address). In the UK, a "ton" is 2240 lbs, period. A "short ton" is 2000 lbs. In the US/Canada, a "ton" is 2000 lbs, while a "long ton" is 2240.
The "long" imperial (British) ton of 2240 lbs, and the "short" ton of 2000lbs as used by America!
So the conventional wisdom can be right in both instances.....as long as they don't get mixed, as in the British billion, and the American billion - I think yours is only 1,000 million, while ours is 1 million million!
And so it goes on - you sat poe-tah-toe and I say poe-tay-toe, you say toe
-may-toe, and I say toe-mah-toe :)
Two countries divided by an uncommon language! (etc!)
Did you get the e-mail I sent about where I got my iron ore? Also, re-reading Ron's post, he didn't say you were wasting your time. He was very supportive of my quest for iron ore, letting me know exactly where there was magentite sand I could harvest. Hope you have as much fun smelting the ore as I did. Todd
Troy units are extraneous to this discussion, unless there is a ton unit in the troy system.
Many words have more than one meaning. The relevant meaning in any particular situation is discerned by considering the context. I believe that my last sentence in the quote above makes quite clear the meaning that I had in mind. If you had trouble discerning the meaning, perhaps you should question *your* education rather than mine.
And your point is? I didn't say there wasn't a "metric ton force" unit; I merely said that the "metric ton" unit was a measure of mass.
That's all very interesting, but it is at odds with widespread practice in many areas of engineering, where a pound-force is commonly referred to simply as a pound, while a pound-mass is referred to explicitly as a pound-mass. Taking a quick glance in a few books from my shelf, I see that all of the following specify the pound as the unit of force (i.e., in the U.S.Customary and British systems); the unit of mass is specified as either the pound-mass or the slug:
- "An Introduction to the Mechanics of Solids" (2nd ed., Crandall, et al)
- "Aerodynamics, Aeronautics, and Flight Mechanics" (McCormick)
- "Fluid Mechanics" (6th ed, Streeter & Wylie)
- "Engineering Mechanics" (2nd ed, Higdon, et al)
- "Vector Mechanics for Engineers" (3rd ed, Beer & Johnston)
The only exception I found was in a British book ("Basic Ship Theory", Rawson & Tupper), which refers to the pound as the unit of mass and the pound-force and poundal as the units of force.
The "Standard Handbook of Machine Design" (Shigley & Mischke) says "The U.S. Customary System unit of the pound-force is often abbreviated as lbf to distinguish it from the pound-mass, which is abbreviated as lbm. In most places in this book the pound force is usually written simply as the pound and abbreviated as lb." From my experience, this convention is widely adopted in engineering practice.
The American Institute of Aeronautics and Astronautics takes a slightly different tack in their "Aerospace Design Engineers Guide" (3rd ed). In the table of mass units, they include the "pound (avoirdupois)" and the ton, but specify that they "must be used with caution because those units are not properly mass units but weight equivalents, which depend on standard terrestrial acceleration due to gravity (g)." In the table of force units, they include the "pound", along with the poundal and the kilogram-force, but they again caution with regard to all three that "those units are not force units but weight equivalents of mass, which depend on g." [While the standard acceleration may not be "officially" defined in the U.S. Customary system, it is almost universally (as far as I have seen) taken to be the same as the standard SI value, appropriately converted.]
It's all well and good that ASTM, NIST, and NPL prefer the term "pound-force" (and perhaps even specify that term in their standards). Nevertheless (and in spite of historical usage and your contention that it is the pound-force that "ought to be identified as such"), the fact remains that the pound-mass is the term that is "identified as such" in current widespread usage among a large group of professionals who work with these units day in and day out. It may be that in the scientific community there is a preference for the pound-force, but it seems to me that the adoption of SI units is much more pervasive in that community than in the engineering community, so I would wager that the "pound-mass" is in much more common use today than the "pound-force". Certainly in lay terms, "pound" usually refers to pound-force, since it is associated with the values provided by spring-type scales or load-cells, which measure force, not mass.
The ton (primarily the long ton) is used predominantly as a unit of force in the field of naval architecture (ship design), at least in the US. There are a few situations therein where it is used as a unit of mass, but it is typically clear from the context whether it is being used as a mass or force unit. The British book I mentioned earlier refers to a ton-force unit, but I don't recall seeing it used in practice.
As for other uses of the ton as a unit of force, road and bridge capacities are often specified in tons. It seems reasonably likely to me that these are force specifications. On the other hand, I would imagine that in cases such as pollutant discharges and air conditioner capacities, the tons involved are units of mass.
I can't really say whether the ton is used more pervasively as a unit of mass or as a unit of force (or weight). Personally, I have dealt with it much more frequently as a unit of force, but I'll amend my original statement and say that the long ton and short ton could be units of mass -or- units of force. The metric ton is still, as far as I know, used only as a unit of mass.
Well, it may not be "official", but there's a definition that's pretty widely accepted today (I dare say universally accepted, at least in the engineering world).
I don't believe I've ever seen 32.16 ft/s² used as the standard free fall acceleration. In fact, I don't recall ever seeing anything other than the English equivalent of 9.80665 m/s², rounded to the varying extents (32.2, 32.17, 32.174, or 32.1740 ft/s²).
So the question is, when you buy a short ton of steel, are you buying a short-ton-mass or a short-ton-force? In the case of scrap, at least, I would contend that you're buying a short-ton-force, since you're most likely measuring the quantity using a device that senses force. Of course, in practical terms, the quantity you end up with will be the same whether it's specified as a ton-mass or a ton-force, as long as the scale is properly calibrated.
On the contrary, they are very relevant to your erroneous assumptions that calling something a "unit of weight" implies that it is a unit of force and that it is not a unit of mass. This applies whether the units are "tons" or "ounces" or anything else.
But by the time you entered the discussion it had generalized and didn't specify any specific context. Therefore you need to consider all the possibilities.
BTW, in the United States that iron ore discussed by the OP had its production figures reported by the U.S. Bureau of Mines (or whatever the agency is called that issues the annual production reports) in _long_ tons, before they switched to _metric_ tons in the 1960s or
1970s. Short tons have never been used for iron ore production in the United States.
I wasn't talking about any meaning you had in mind, because that isn't what led you astray. It was your failure to understand how others use this word that was your downfall. (Technically, "others" is too broad, because it is clear from your overall comments that you don't really understand how you use the word yourself either.)
Besides, you only used the verb form, and there are big differences in the use of the verb form and the noun form
You quite clearly implied both that the metric ton is not a unit of force, and that the long ton and the short ton are not units of mass. There is no other way to interpret your "technically speaking" remark, is there?
If you are now retracting those claims, say so.
That it is widespread does not save it from being fooling.
Now, go to the grocery store and see exactly how many of the items you see pounds on there, and tell me exactly how many of them identify these pounds as pounds-mass. Exactly zero, I'll bet.
Engineers also call it a pound of sugar or a 20 lb pumpkin, without identiying the pounds in this case either.
Furthermore, the foolishness is epitomized by the rocket scientists and engineers, who get specific impulse in "seconds" by failing to distinguish between the pounds force in the thrust and the pounds mass in the fuel consumption rate. The proper SI units of specific impulse, for example, are newton seconds per kilogram (or the equivalent meters per second). Note also that the equally foolish Russian rocket scientists and engineers in the old days before they started using newtons a decade or so ago used to get the same pseudoseconds units by confusing kilograms force and kilograms mass.
Do they cite any authority for this claim? I bet not.
It's nothing but unsupported babble by another miseducated fool.
Do they tell you what the standard for these pounds is? Can you tell us what it is, whether they did or not? What is the nature of this standard? Something electrical, or mechanical, or what? Who made it the standard, and when? Tell me the year if you can, or a range of years if that is the best you can do. To whom does that standard apply? Where is the standard kept, and who maintains it?
False.
Units of mass. That's what is measured at the "weigh stations" you see along the road, and that's what the truck drivers know.
American Society for Testing and Materials, Standard for Metric Practice, E 380-79, ASTM 1979:
3.4.1.5 The term load means either mass or force, depending on its use. A load that produces a vertically downward force because of the influence of gravity acting on a mass may be expressed in mass units. A load that produces a force from anything other than the influence of gravity is expressed in force units.
The tons used in air conditioner capacities are neither units of mass nor units of force, but rather units of power equal to 12000 Btu/h, and other refrigerator tons are units of energy.
They are loosely based on some ton as a unit of mass, not a ton-force.
I have seen a couple of physics textbooks using this value, e.g. J. Edmond Shrader, Physics for Students of Applied Science, McGraw Hill,
1st ed., 1937.
Units of Force. Until a system of units has been established, Newton's second law may be expressed by the equation F = kma, where k is the proportionality factor between the force and the product ma. By setting certain values for F as related to m and a, k may be determined, and a system of units for force may be established. In fact, by two different conditions of determining k, two systems in both the British and the metric systems have been adopted. In the metric system . . . In the same manner, the British unit of force, called the poundal, was established under the conditions that F was expressed in poundals, when m was measured in pounds, and a in feet per second per second. These units of force are called the absolute c.g.s. unit or absolute f.p.s. unit, as the case may be. These systems are termed absolute because they are expressed in fundamental units which are not subject to variation. Opposed to the absolute system is the gravitational system of units of force. This is based upon the value of the acceleration due to gravity. Since the acceleration of gravity varies from place to place on the earth's surface, it is readily seen that the gravitational unit of force is a variable quantity unless some specific value of g is adopted. The value of g used is that at latitude 45° at sea level. This value is 32.16 ft./sec.², or 32 ft./sec.², approximately. The gravitational unit of force in the British system is established as follows: The unit of force is called the pound when the mass acted upon is 1 lb., and the acceleration is that due to gravity g measured in feet per second per second. Under these conditions (1 lb. force) = k × (1 lb. mass) × (g × ft./sec.²)
But where it is still most noticable today is in the kinetic energy formulas used in ballistics in a foot-grain-second-pound force system, with E = m·v²/450240 for this value for g_n = 32.16 ft/s². Just search the Internet and Usenet for the number in the denominator, and you will see that it is very much in use. (You can also find the value in the numerator corresponding to the standard acceleration of free fall which defines grams force, 450437, or also 450436 when there is some intermediate rounding.)
Wrong. How it is measured is of little importance. The real question is, if you are the seller and you are charged with giving short weight, how will that fact be established? It won't be on the basis of your measurement, but rather on someone else's measurement of mass, on a tested and certified scale..
Of course, if your scale is tested and certified for use for this purpose, it will also be tested for its accuracy in measuring mass in the location in which it is used--not for its accuracy in measuring force.
If it is properly calibrated, it is calibrated for the measurement of mass in the location in which it is used. You never determine how much force it is exerting in that location--what you measure is the mass. It is a ton-mass, whether you are using long tons or short tons or metric tons.
Now, did you answer the question above, about the standard for a pound which would justify the claims in AIAA "Aerospace Design Engineers Guide"? If not, go back and do so.
What is that standard? Were you able to find anything about it?
Then read the current U.S. law defining the pound, and the discussion of the prior U.S. law and the international agreement of 1959 which means the same definition is used throughout the world, at
formatting link
Note that the U.S. national standards laboratory--then the National Bureau of Standards, later renamed the National Institute of Standards and Technology--sets the standards for science and technology, as well as for commerce.
In academic terms yes, but for practical purposes it appears that only the US version and the metric version remain. As far as I am aware, all UK applications use the tonne of 1000 kg regardless of how it is spelt or pronounced.
Quite. In order to communicate, we need a set of units that are the same in the US and the UK.
Well,the idea was to puddle some iron. As in primitive metallurgy, before anyone knew the word. I've followed up on all the recommendations suggested, e-ing both the American and the Canadian ore associations,several of the large mining companies and the University of Toronto. The one thing even I won't do is walk up and down hills dragging a magnet. That would make me a crank. I'm not a crank.I'm an eccentric
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