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Log Peridic 50m - 1300m
Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz,
(Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH |
Log Peridic 50m - 1300m
The KMA log antennas seem more durable than Create or Tennadyne but not
sure about 80mph wind + ice. They can make you one from thicker materials that would probably survive. Bob Howard W3CQH wrote: Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz, (Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH |
Log Peridic 50m - 1300m
Dear Howard W3CQH:
A 26:1 frequency range is difficult to do well. Might you intend 500 MHz to 1300 MHz? A 2.6:1 LPDA is reasonably straight forward with design information in the ARRL Antenna Handbook (including mechanical information). Use care when specifying survival of an antenna in terms of MPH. It is the equivalent Newtons per square meter (pounds-force per square foot) that is important. Several ways of describing wind speed exist and are not equal in terms of what they do to an antenna structure. Ask for pressure information. I do not recognize the "30 Lb of ICE" specification. Most often, ice loading is specified in terms of size such as 12 mm of ice all of the way around each element (12 mm of radial ice). It will help to know the task to be performed by the antenna. Tell us more. Regards, Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Howard W3CQH" wrote in message ... Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz, (Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH |
Log Peridic 50m - 1300m
On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin"
wrote: I do not recognize the "30 Lb of ICE" specification. Most often, ice loading is specified in terms of size such as 12 mm of ice all of the way around each element (12 mm of radial ice). Given the looseness of use of the unit lb to specify mass and (incorrectly) force, it is a bit ambiguous... but he probably means mass. 30lbf of windage from ice loading isn't much on an antenna of that type! (We sin in the metric system as well! If someone asks me what I weigh (being a force) I will answer in Kg (being a mass) instead of N (force).) Having said that, the impact of ice on the wind forces is probably much more significant than the gravitational force due to the mass of the ice. Mac, I agree, radial ice loading is a more relevant specification. Owen -- |
Log Peridic 50m - 1300m
"Howard W3CQH" wrote in message ... Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz, (Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH http://www.eham.net/reviews/detail/1700 for starters |
Log Peridic 50m - 1300m
"Owen Duffy" wrote in message ... On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin" wrote: I do not recognize the "30 Lb of ICE" specification. Most often, ice loading is specified in terms of size such as 12 mm of ice all of the way around each element (12 mm of radial ice). Given the looseness of use of the unit lb to specify mass and (incorrectly) force, it is a bit ambiguous... but he probably means mass. lbs is always force as far as i know. slugs is mass. so long as we are confined to the planet earth, there is no difference really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go to the moon ... kilogram, slug -- mass newton, pound -- force Gravity 30lbf of windage from ice loading isn't much on an antenna of that type! (We sin in the metric system as well! If someone asks me what I weigh (being a force) I will answer in Kg (being a mass) instead of N (force).) Having said that, the impact of ice on the wind forces is probably much more significant than the gravitational force due to the mass of the ice. Mac, I agree, radial ice loading is a more relevant specification. Owen -- |
Log Peridic 50m - 1300m
Dear Owen:
As you, and others, have concluded from my descriptions, I too have mass and force in separate bins. I continue to be amazed at the facility with which MEs use "pounds" to indicate just what they want it to indicate. Every time that I do a mechanical design (or check a mechanical design), I convert to SI units with a careful check accompanying the conversion of whether I have converted forces or masses. Once in SI, everything is easy. I have had discussions with some of my fellow P.E.s of the ME persuasion about this: they contend that they always know when force and mass is involved. I remain unconvinced. A mass centered system (SI) is more straight forward than a force centered system where an assumed gravitational field is used. Here in the North, ice plus a moderate amount of wind is most often what kills antennas having cantilevered elements. Thanks for your comments. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Owen Duffy" wrote in message ... On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin" wrote: I do not recognize the "30 Lb of ICE" specification. Most often, ice loading is specified in terms of size such as 12 mm of ice all of the way around each element (12 mm of radial ice). Given the looseness of use of the unit lb to specify mass and (incorrectly) force, it is a bit ambiguous... but he probably means mass. 30lbf of windage from ice loading isn't much on an antenna of that type! (We sin in the metric system as well! If someone asks me what I weigh (being a force) I will answer in Kg (being a mass) instead of N (force).) Having said that, the impact of ice on the wind forces is probably much more significant than the gravitational force due to the mass of the ice. Mac, I agree, radial ice loading is a more relevant specification. Owen -- |
Log Peridic 50m - 1300m
On Sun, 18 Jun 2006 07:10:56 -0500, "gravity"
wrote: Given the looseness of use of the unit lb to specify mass and (incorrectly) force, it is a bit ambiguous... but he probably means mass. lbs is always force as far as i know. slugs is mass. so long as we are confined to the planet earth, there is no difference really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go to the moon ... kilogram, slug -- mass newton, pound -- force I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. Practice may be different in different places, but I suspect that it is laxness on the part of practitioners who refer to force in units of pounds. I just had a look at Wikipedia (which isn't the oracle), here is their summary: "The pound is the name of a number of units of mass, all in the range of 300 to 600 grams. Most commonly, it refers to the avoirdupois pound (exactly 453.59237 g), divided into 16 avoirdupois ounces. There is also a unit of force corresponding to the avoirdupois pound, see pound-force." Wikpedia highlights just another aspect of the unit, its flexibility! Owen PS: a slug is a unit of mass, and equivalent to about 14.6Kg or 32.2lbs. I don't think it is in wide use! -- |
Log Peridic 50m - 1300m
Owen Duffy wrote:
I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. When you are doing physical calculations it is very important to use the correct units, other wise you calculations are meaningless. Suppose you want to know what you will weigh on the moon where the acceleration due to gravity is 5.25 ft/sec^2. F = M*A if you use 200 for your mass you get, 200 * 5.25 = 1050, that indicates you would weigh 1050 lbs on the moon. Which is clearly wrong. Trying again with the correct units and you get, 6.25 * 5.25 = 32.8, now that sounds more like what you would weight on the moon. In the non scientific world, where the metric unit KG is used for weight, M=F*A works just fine if you put what you call "weight" in KG in for M in the formula. It's arguable which method is better, using mass or force units for weight. What you want to know is do you need to change your weight, if the doctor tells you that you need to loose weight, that's easy just move to the moon, done. What he really wants is for you to loose mass. So your weight (force) can change with gravity, but your mass doesn't change. Unless of course you loose weight ;) -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
On Mon, 19 Jun 2006 13:03:02 -0500, Chris W wrote:
the doctor tells you that you need to loose weight, that's easy just move to the moon, done. Hi Chris, Language is a strange thing. For instance the doctor would probably prescribe a laxative if he wanted you to loose weight. 73's Richard Clark, KB7QHC |
Log Peridic 50m - 1300m
"Chris W" wrote in message news:rFBlg.57799$9c6.28215@dukeread11... Owen Duffy wrote: I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. F = MA F = 1 pound * 32 feet/s^2 F = 32 pound*feet/s^2 you will note that pound(mass)* feet/s^2 is NOT the pound force unit. the pound force unit is slug*feet/s^2. there is nothing wrong with the pound mass unit per se. you alluded to slugs. F = MA F = 1 slug * 32 feet/s^2 F = 32 slugs*feet/s^2 = 32 pounds anyone else having flashbacks to particle dynamics class? Gravity So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. When you are doing physical calculations it is very important to use the correct units, other wise you calculations are meaningless. Suppose you want to know what you will weigh on the moon where the acceleration due to gravity is 5.25 ft/sec^2. F = M*A if you use 200 for your mass you get, 200 * 5.25 = 1050, that indicates you would weigh 1050 lbs on the moon. Which is clearly wrong. Trying again with the correct units and you get, 6.25 * 5.25 = 32.8, now that sounds more like what you would weight on the moon. In the non scientific world, where the metric unit KG is used for weight, M=F*A works just fine if you put what you call "weight" in KG in for M in the formula. It's arguable which method is better, using mass or force units for weight. What you want to know is do you need to change your weight, if the doctor tells you that you need to loose weight, that's easy just move to the moon, done. What he really wants is for you to loose mass. So your weight (force) can change with gravity, but your mass doesn't change. Unless of course you loose weight ;) -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
Chris W wrote: Owen Duffy wrote: I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. . . That's 6.25 pounds mass, I presume, for someone weighing 200 pounds force. In my entire engineering school curriculum, I had only two courses which didn't use the metric system, Statics and Dynamics, taught by the civil engineering department. I have vague recollections of pounds force, pounds mass, slugs, and poundals. As often as not, my answers were off by g^2, since I never could remember which ones already had gravitational acceleration built in and which didn't. But I developed a method to deal with it. When presented with a problem, I first converted everything to SI units. Then I solved the problem and converted the answer back to U.S. units. What a horrible system! My hat's off to the Canadians, who had the will to convert, and established -- and stuck with -- a systematic program to do it. What the U.S. did was to declare the metric system to be official ("Mission Accomplished!") and change whiskey bottles from fifths to 750 ml (which was promoted by the booze industry because it made the bottles just a little smaller and they could charge the same price). Wow. Roy Lewallen, W7EL |
Log Peridic 50m - 1300m
"Owen Duffy" wrote in message ... On Sun, 18 Jun 2006 07:10:56 -0500, "gravity" wrote: Given the looseness of use of the unit lb to specify mass and (incorrectly) force, it is a bit ambiguous... but he probably means mass. lbs is always force as far as i know. slugs is mass. so long as we are confined to the planet earth, there is no difference really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go to the moon ... kilogram, slug -- mass newton, pound -- force I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. Practice may be different in different places, but I suspect that it is laxness on the part of practitioners who refer to force in units of pounds. I just had a look at Wikipedia (which isn't the oracle), here is their summary: "The pound is the name of a number of units of mass, all in the range of 300 to 600 grams. Most commonly, it refers to the avoirdupois pound (exactly 453.59237 g), divided into 16 avoirdupois ounces. There is also a unit of force corresponding to the avoirdupois pound, see pound-force." Wikpedia highlights just another aspect of the unit, its flexibility! Owen PS: a slug is a unit of mass, and equivalent to about 14.6Kg or 32.2lbs. I don't think it is in wide use! -- i first heard of slugs at age 7, but i've never seen them used in an engineering class. we used SI almost exclusively in university and high school. i was taught there that pounds is a unit of force (not mass). however Wikipedia claims pounds is a standardized unit of mass, not force. so we are both right really. as i've noted in another post, 1 slug at in Earth's gravitational field is ~ 32 pounds, so it's a convenient unit to use. so basically if NIST (or whoever) defines it as mass, then we are stuck with it. "honey do i look fat in this dress?" "no baby, you are no more than 5 slugs or so." Gravity |
Log Peridic 50m - 1300m
Roy Lewallen wrote:
Chris W wrote: Owen Duffy wrote: I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. . . That's 6.25 pounds mass, I presume, for someone weighing 200 pounds force. No, it is 6.25 slugs of mass. There is no such thing as pounds of mass. Sorry for leaving off the units in my last post. Just because someone says x KG of force or x lbs of mass doesn't mean that KG can be force and pounds can be mass. Distance: Meter, Feet Force: Newton, Pound Mass: KG, Slug Time: Second, Second (Can you imagine if there were different time units in each system?) All other units are derived from these. Actually Newtons and Pounds can be derived from time, mass and distance. 1 newton = 1 KG*M/s^2 and 1 pound = 1 slug*ft/s^2. Which brings us right back to that fundamental formula F = M*A, 200 lbs = 6.25 slugs * 32 ft/sec^2. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
gravity wrote:
i first heard of slugs at age 7, but i've never seen them used in an engineering class. we used SI almost exclusively in university and high school. i was taught there that pounds is a unit of force (not mass). however Wikipedia claims pounds is a standardized unit of mass, not force. I don't care who says pounds is a unit of mass, they are wrong! If you use pounds in a formula that wants mass, your answer will be WRONG. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
Thanks to all that have answered my original post - but the information that
I seek has not been answered. I understand that section 207 of the FCC telecomm act 1996 contains information that I might be able to use to help me in this matter. Where can I obtain a copy of Section 207? I cannot find it posted on the FCC website! Thanks, "Howard W3CQH" wrote in message ... Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz, (Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH |
Log Peridic 50m - 1300m
"Chris W" wrote in message news:z8Dlg.57804$9c6.44111@dukeread11... Roy Lewallen wrote: Chris W wrote: Owen Duffy wrote: I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. . . That's 6.25 pounds mass, I presume, for someone weighing 200 pounds force. No, it is 6.25 slugs of mass. There is no such thing as pounds of mass. please read Wikipedia. Owen is correct. pounds are firstly a unit of mass, and secondly a unit of force. Wikipedia cites several sources. 200 pounds of mass weighs approximately 200 pounds of force on the surface of Earth. 1 slug is 32 pounds of force on the Earth. pounds-mass is standardized to kilograms, which are in turn standardized to an alloy bar or other methods. Gravity Sorry for leaving off the units in my last post. Just because someone says x KG of force or x lbs of mass doesn't mean that KG can be force and pounds can be mass. Distance: Meter, Feet Force: Newton, Pound Mass: KG, Slug Time: Second, Second (Can you imagine if there were different time units in each system?) All other units are derived from these. Actually Newtons and Pounds can be derived from time, mass and distance. 1 newton = 1 KG*M/s^2 and 1 pound = 1 slug*ft/s^2. Which brings us right back to that fundamental formula F = M*A, 200 lbs = 6.25 slugs * 32 ft/sec^2. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
everyone who is arguing that pounds is not a unit of mass, please see:
https://carnot.physics.buffalo.edu/a.../msg00062.html this post cites a NIST publication, which is definitive for the USA. there is no room for argument. if you don't live in the USA, well a pound can be anything you wish it to be. Gravity |
Log Peridic 50m - 1300m
"Chris W" wrote in message news:zcDlg.57805$9c6.18712@dukeread11... gravity wrote: i first heard of slugs at age 7, but i've never seen them used in an engineering class. we used SI almost exclusively in university and high school. i was taught there that pounds is a unit of force (not mass). however Wikipedia claims pounds is a standardized unit of mass, not force. I don't care who says pounds is a unit of mass, they are wrong! If you use pounds in a formula that wants mass, your answer will be WRONG. please read the NIST publications which define the Avoirdupois pound in terms of kilograms. this is not debateable since NIST is *the* authority in the US. Gravity -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
gravity wrote:
please read the NIST publications which define the Avoirdupois pound in terms of kilograms. this is not debateable since NIST is *the* authority in the US. The NIST publications define the numeric conversion factors, not the legality for use of any particular terminology. The approximate conversion factor for a pound (mass) is 0.4535924 kilogram. The approximate conversion for a pound (force) is 4.448222 newton. The gravitational acceleration, small g, is defined as exactly 9.80665 in SI units, but it is not similarly defined in inch/pound units. Interestingly enough, however, is that the ratio of pound-force per pound (lbf/lb) (thrust to mass ratio) is exactly converted to newton per kilogram (N/kg) by the factor 9.80665. The position of the US Government can be summarized from the following excerpt found in Federal Standard 376B, Preferred Metric Units for General Use by the Federal Government. In the intro to the section on mass there is a note that says, *** There is ambiguity in the use of the term "weight" to mean either force or mass. In general usage, the term "weight" nearly always means mass and this is the meaning given the term in U.S. laws and regulations. Where the term is so used, weight is expressed in kilograms in SI. In many fields of science and technology the term "weight" is defined as the force of gravity acting on an object, i.e., as the product of the mass of the object and the local acceleration of gravity. Where weight is so defined, it is expressed in newtons in SI. *** The document then goes on to show many conversion factors from both pounds (mass) and pounds (force) to SI units. No indication that one is more legal or correct than the other. Soooo, use pounds any way you wish; just do the math correctly. 73, Gene W4SZ |
Log Peridic 50m - 1300m
On Mon, 19 Jun 2006 12:01:37 -0700, Roy Lewallen
wrote: do it. What the U.S. did was to declare the metric system to be official ("Mission Accomplished!") and change whiskey bottles from fifths to 750 ml (which was promoted by the booze industry because it made the bottles just a little smaller and they could charge the same price). Wow. Roy, you overlooked that the US, an earlier signup to SI, fixed the spelling of metre in the US variant of SI. Owen -- |
Log Peridic 50m - 1300m
Dear Howard W3CQH:
You have not been clear about what information you need. What do you wish to accomplish? Here is Section 207: Telecommunications Act of 1996 SEC. 207. RESTRICTIONS ON OVER-THE-AIR RECEPTION DEVICES. Within 180 days after the date of enactment of this Act, the Commission shall, pursuant to section 303 of the Communications Act of 1934, promulgate regulations to prohibit restrictions that impair a viewer's ability to receive video programming services through devices designed for over-the-air reception of television broadcast signals, multichannel multipoint distribution service, or direct broadcast satellite services. It sure is not clear what this has to do with what you have said so far. ...... and, in "real" engineering: Kg is the unit of mass in the SI mks system. Newton is the unit of force. F does equal MA (at least for low velocities). 73 Mac, N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Howard W3CQH" wrote in message ... Thanks to all that have answered my original post - but the information that I seek has not been answered. I understand that section 207 of the FCC telecomm act 1996 contains information that I might be able to use to help me in this matter. Where can I obtain a copy of Section 207? I cannot find it posted on the FCC website! Thanks, "Howard W3CQH" wrote in message ... Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz, (Ham variety). Specs must also contain that it can withstand 80MPH wind and 30 Lbs of ICE? Thanks and best DXin. de Howard W3CQH |
Log Peridic 50m - 1300m
gravity wrote:
please read the NIST publications which define the Avoirdupois pound in terms of kilograms. this is not debateable since NIST is *the* authority in the US. The NIST isn't the authority on the laws of physics. One of the most basic of which is F=MA, if you use pounds for mass in that formula you get the wrong answer. Nothing that NIST says will change that. 200 lbs = 6.25 slugs * 32 ft/sec^2. Using pounds, the formula won't work any other way. -- Chris W KE5GIX Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, from anywhere, for any occasion! http://thewishzone.com |
Log Peridic 50m - 1300m
Chris W wrote: Owen Duffy wrote: I was taught (in imperial units) to differentiate mass (pound) and force (pound-force). That learning stood me well when we changed to SI (metric) part way through school. You were taught wrong. If you use pounds in a formula that wants mass such as F=M*A you will get the wrong answer. So lets say you weigh 200 lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by solving for M = F/A or 200/32 = 6.25. If you "weigh" 200 lb (no s at the end of unit symbols) on Earth, that _is_ your mass, in normal usage in either the medical sciences or in sports, which are of course the purposes for which we normally weigh ourselves. You can, of course, use those 200 pounds in the F = ma formula. For example, if you accelerate those 200 pounds at 40 ft/s², the force is 8000 lb·ft/s², which is, of course, 8000 poundals, since a poundal is the force which will accelerate a mass of one pound at a rate of 1 ft/s². When you are doing physical calculations it is very important to use the correct units, other wise you calculations are meaningless. Suppose you want to know what you will weigh on the moon where the acceleration due to gravity is 5.25 ft/sec^2. F = M*A if you use 200 for your mass you get, 200 * 5.25 = 1050, that indicates you would weigh 1050 lbs on the moon. Which is clearly wrong. Trying again with the correct units and you get, 6.25 * 5.25 = 32.8, now that sounds more like what you would weight on the moon. Not at all. It indicates that you exert a force due to gravity of 1050 poundals (not lbs) on the moon. On Earth, you would exert a force of somewhere in the neighborhood of 6410 poundals to 6450 poundals, depending on your specific location. Not only is it just as easy to use an unfamiliar unit for force as it is to use some strange unit for mass, but the absolute foot-pound-second system (which includes poundals) has been around considerably longer than the gravitational foot-pound-second system (which includes slugs), and rather than either of those systems, those still using English units are more likely to use the engineering system which includes both pounds and pounds force, but neither slugs nor poundals. Since that system is not a completely coherent system, of course, many of the formulas need to be adjusted with a g_c factor, a dimensionless number equal to the ratio of the acceleration used to define a pound-force to that used to define a poundal, or g_c = (32.174 ft/s²)/(1 ft/s²) = 32.174 In the non scientific world, where the metric unit KG is used for weight, M=F*A works just fine if you put what you call "weight" in KG in for M in the formula. The symbol for kilograms is kg, not KG. There is nothing different about the weight in the English units world, where the pound used for this purposes is, by definition, exactly 0.45359237 kg. Gene Nygaard |
Log Peridic 50m - 1300m
Chris W wrote: gravity wrote: please read the NIST publications which define the Avoirdupois pound in terms of kilograms. this is not debateable since NIST is *the* authority in the US. The NIST isn't the authority on the laws of physics. One of the most basic of which is F=MA, if you use pounds for mass in that formula you get the wrong answer. Nothing that NIST says will change that. 200 lbs = 6.25 slugs * 32 ft/sec^2. Using pounds, the formula won't work any other way. Bull****. Here are a couple of other ways that work just fine with FFU: 200 lb * 32.2 ft/s² = 6440 pdl 0.52 slinch * 386 in/s² = 200 lbf Be sure to distinguish pounds force (lbf) from pounds (lb), and units of measure should remain unchanged in the plural, without adding any language-specific "s" or whatever. Gene Nygaard |
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