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#1
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On Wed, 01 Oct 2003 10:32:56 -0700, Jim Kelley
wrote: Gene Nygaard wrote: They are incorrect in the doctor's office, and even more incorrect in the supermarket or the jewelry store. Like I said, you don't have to call the quantities used there "weight"--but if you do call them weight, use the definition which is correct in that context. Don't misinterpret what is being used there. Do you know what you're talking about Gene? Cuz I sure don't. It's generally accepted that weight is a force. I've shown in this thread from the experts in the field, including NIST (the U.S. national standards agency) and ASTM (an industry standards agency) and NPL (the U.K. national standards agency) and the Canadian Standard for Metric Practice, that this is false. I don't agree. All of these sources and many others tell you that weight is an ambiguous word, with several different meanings. What physical quantity do you think a grocery store scale measures? You can probably figure that out for yourself, if you stop to think about how they are tested and certified. Especially if you have enough common sense to figure out that when we buy and sell goods by weight, we wouldn't want to measure some quantity that varies with location. Another big clue is the units in which that quantity is measured; grams in most of the world, and at least on prepackaged goods in the United States. In that regard, you might also consider how the law defines a pound (i.e., 0.45359237 kg), and then ask youself why in the world the law bothers defining a pound in the first place. When I was a kid, almost all the scales in the grocery stores were balances. You do understand what Richard Clark, among others, has told us about what we measure with those balances, don't you? Sure, they had evolved to the point where you didn't have to place loose, individual weights on a pan to get them to balance. The store we used most often had one with a dial readout, and a computing scale listing total price based on various prices per pound, but it prominently displayed the company motto on the side facing the customer: HONEST WEIGHT NO SPRINGS That scale wouldn't give you any different reading atop Mt. Chimborazo or at the North Pole than it did in the store in which it was used. Now, after the invention of the microprocessor, we have other options with reasonable cost and performance to accomplish the same thing. Problems can arise when someone claims a mass is a force and vice versa. I agree. And so a torque wrench has what kind of units printed on its scale - mass and distance, or force and distance? Once again, it doesn't cost you any more to pay attention. Like I told you a long time ago, my torque wrench has "meter kilograms" on it. What does that tell you? Why didn't you answer me then? Message-ID: Date: Fri, 26 Sep 2003 23:35:11 GMT Though I have had mine for several years, such torque wrenches, of course, are still readily available. http://jcwhitney.com/webapp/wcs/stor...&storeId=10101 They are units of force and distance, if you can't figure it out, just as the "foot pounds" which are the other units on my wrench are. But just as the existence of the kilogram force does not prove that pounds are not units of mass, the existence of pounds force does not prove that pounds are not units of mass. You could, of course, argue that we should all change to your usage. Many people already have, obviously. Not very many, surprisingly. Just the ones who write physics books maybe? It is much more common to find people claiming, erroneously, that there is some error in that usage. You're the first guy I've ever seen making claims about errors in usage. Like slugs, poundals only exist in one limited purpose system of mechanical units, mostly used to simplify calculations. But you'd like us to believe the unit of mass in that system is ubiquitous and universal, and that everybody is wrong! The pound, of course, like the foot and the second, predates that system, and those units are all used in many other systems as well as outside any such specialized system. IIRC, there is only at most one unit in any of the commonly used specialized systems of English mechanical units that was invented specifically for use in that system: the poundal in the absolute fps system, the slug in the gravitational fps system, the slinch in the gravitational inch-pound-second system. The old metric cgs systems have two mechanical units with special names that aren't in other systems, the dyne and the erg, and of course they also have various names in the different flavors of cgs for electrical and magnetic units, quantities that have never been measured in English units. Of course, you also have combinations involving those units, such as foot-poundals. That the poundal system is much older than the slug system is merely one of the many clues as to which is older, the pound mass or the pound force. Gene Nygaard http://ourworld.compuserve.com/homepages/Gene_Nygaard/ |
#2
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Gene Nygaard wrote: What physical quantity do you think a grocery store scale measures? You can probably figure that out for yourself, if you stop to think about how they are tested and certified. You misunderstand, Gene. It's not at all clear what _you_ think they measure. I'm not asking about the units displayed on them. What physical quantity do you think is actually being measured? And so a torque wrench has what kind of units printed on its scale - mass and distance, or force and distance? Once again, it doesn't cost you any more to pay attention. They are units of force and distance, There's the point. That the poundal system is much older than the slug system is merely one of the many clues as to which is older, the pound mass or the pound force. Ah, older. So that means.........what? 73, Jim AC6XG |
#3
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On Thu, 02 Oct 2003 09:25:38 -0700, Jim Kelley
wrote: Gene Nygaard wrote: What physical quantity do you think a grocery store scale measures? You can probably figure that out for yourself, if you stop to think about how they are tested and certified. You misunderstand, Gene. It's not at all clear what _you_ think they measure. I'm not asking about the units displayed on them. What physical quantity do you think is actually being measured? I think that is probably obvious to anybody with half a brain. But it really doesn't matter, that shouldn't be any impediment to your telling us where my clues have led you. Where are you trying to lead me? Maybe you have some strange notion of what the verb "to measure" means? It wouldn't hurt you to stop and reflect on that for a moment, and answer it at least to yourself, before you get to the "Open mouth, insert foot" stage. And so a torque wrench has what kind of units printed on its scale - mass and distance, or force and distance? Once again, it doesn't cost you any more to pay attention. They are units of force and distance, There's the point. Why are you still refusing to deal with the "meter kilograms" on my torque wrench, even going so far as to dishonestly snip that out from the middle of what you quoted, in between your own comments, without telling us that you were doing so? Since this involves only force and distance, what could it possibly tell you about the existence of a unit of mass called a kilogram? Since this involves only force and distance, what could it possibly tell you about the existence of a unit of mass called a pound? That the poundal system is much older than the slug system is merely one of the many clues as to which is older, the pound mass or the pound force. Ah, older. So that means.........what? Let's not overlook the obvious. Perhaps most the most important thing for your education, and that of several other fools in this thread as well, that it exists. That's something you weren't willing to admit in the beginning. But if it didn't exist, we certainly wouldn't be able to say that it is older. (A corollary, of course, is that if pound force didn't exist, there would be nothing for these units to be older than.) Thus, what you quoted from the appendix of Halliday and Resnick (1981) was incorrect. Do you agree? That it is legitimate. Conversely, that it is the pound force that is the ******* child. This is also one important factor in the usage rules as spelled out by the ASTM and followed by NIST, the U.S. national standards laboratory, and the National Physical Laboratory, the U.K. national standards laboratory. That is indeed one reason why this unit gets to use the unadorned name "pound" and the original symbol "lb," while the newer spinoff needs to be identified as a "pound force" and use the symbol "lbf" to distinguish itself. That the troy pounds, in terms of which the avoirdupois pound was defined for centuries, are units of mass. This doesn't tell you that they have never spawned units of force of the same name; you have to figure that fact out by other means. Gene Nygaard http://ourworld.compuserve.com/homepages/Gene_Nygaard/ |
#4
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Gene Nygaard wrote:
"Why are you still refusing to deal with the "meter kilograms" on my torque wrench---?" Multiply the meters by 3.28 and multiply the kilograms by 2.2, and you will have torque in their product computed in foot pounds. Or, just multiply the dial reading by 7.22 for ft.lbs. Torque is the product of force and distance. Weight is a force produced by gravity on a particular mass. The indication on a torque wrench is muscle force times lever length. It directly has little relation to gravity in most torque wrench applications. Weight is the easy way to determine mass. Computing mass from collection of acceleration data would be more complicated. M = F/A Best regards, Richard Harrison, KB5WZI |
#6
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Gene Nygaard wrote: It's Jim Kelley who is having great difficulty dealing with these "meter kilograms." Their existence demolishes one of his major arguments. Will he, or any of the others making similar foolish arguments, ever address this? If you have a point, sir, I think it's time you should make it. If your intent is nothing more than to blither inanities, then when will you have your fill? 73 de ac6xg |
#7
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On Fri, 03 Oct 2003 11:01:09 -0700, Jim Kelley
wrote: Gene Nygaard wrote: It's Jim Kelley who is having great difficulty dealing with these "meter kilograms." Their existence demolishes one of his major arguments. Will he, or any of the others making similar foolish arguments, ever address this? If you have a point, sir, I think it's time you should make it. If your intent is nothing more than to blither inanities, then when will you have your fill? You can be pretty dense when you want to be. Here's what you, Jim Kelley, wrote earlier in this thread: Date: Fri, 26 Sep 2003 15:44:09 -0700 Message-ID: Why do you think torque wrenches have the unit 'foot-pounds' printed on them if the pound is a unit of mass? Date: Wed, 01 Oct 2003 10:32:56 -0700 Organization: University of California, Irvine Lines: 53 Message-ID: And so a torque wrench has what kind of units printed on its scale - mass and distance, or force and distance? What was your point in asking these questions? Quite simple. You were offering those "foot-pounds" as proof of the supposed fact that pounds are units of force and not units of mass. In fact, you specifically claimed, by asking a rhetorical question in last Friday's message, that torque wrenches would not have these units on them if a pound is a unit of mass. So my followup to you is along the same lines: Do you claim that those "meter kilograms" prove that kilograms are not units of mass? Not a very difficult question to answer, is it, Jim? Gene Nygaard http://ourworld.compuserve.com/homepages/Gene_Nygaard/ |
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