where did KN come from?
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Does anyone know the history of kilo newtons (KN)? Where? How? When? |
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Newton's are a unit of force, named after Isaac Newton. A kilo-Newton is 1000 Newtons. Isaac Newton was the founding father of classical mechanics, so the base unit of force was named after him. He was a giant among giants in the scientific community, arguably one of the greatest mathematical/scientific minds that ever lived. His work has positively impacted the lives of everyone that benefits from any type of modern living.
I guess that covers the "why," which you didn't really ask for. I hope that was useful. |
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Introduced in 1960 under the SI unit system, previously the kilogram force (kgf) was used. |
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A good approximation for 1 kN is 225 lbf, the weight of a big guy. |
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The Bobby wrote:A good approximation for 1 kN is 225 lbf, the weight of a big guy.So if I jump up, I land with the force of 1 Kn? Or do I need to reach terminal velocity? Also, I'll bet the pound is something like the weight of a criminal's hand after being chopped off. |
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Well like others said, one newton is equal to a kg meter per second squared. Seconds are defined by the frequency of cesium atoms. The kilogram is a kind of arbitrary mass roughly related to the density of water but actually defined by a platinum bar in Paris. The problem with that of course is that the bar is slowly losing mass. It's miniscule but still enough to be a worry for very precise physics., |
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The Bobby wrote:Now a harder question: where did pounds come from? :) What a stupid measurement. 1 lb = 6992 troy grains. WTF?1 lb = 1 (slug * ft)/s^2 Now, what the heck is a slug? |
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Mike - It depends on how high you jump. If you have a 37" vertical jump, you should probably try out for the NBA. Otherwise, you would not land w/ a 1 N force. Jumping off anything elevated, however, would quickly get you into multiple N (since its m/s^2). |
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Louis Eubank wrote:The primary reason for using kN is, as has been stated above, it is a measure of force, hence much more useful in dynamic situations than kg (or lbs) would be.Dont you mean that it is more useful than kg (or slugs) since lbs is a measurement of force. |
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Mike Lane wrote: So if I jump up, I land with the force of 1 Kn? Or do I need to reach terminal velocity? Also, I'll bet the pound is something like the weight of a criminal's hand after being chopped off.1 kN is the about the same as a 225lb weight hanging free on a rope, or you(at 225 lbs) standing on the ground. When you jump, or with any dynamic load, things get more complicated. It's not a function of how far you fall as Louis E said, but rather how quickly you slow down. The key point to remember is: F=ma. Your mass is constant, but depending on how much you bend your knees and back, what surface you land on, shoes you're wearing, etc, the acceleration (and therefore force) will vary significantly. Someone summarized the point well by saying: "no one ever got hurt by driving fast, only stopping fast." |
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DrApnea wrote: Dont you mean that it is more useful than kg (or slugs) since lbs is a measurement of force.Despite what we learned in school, the pound avoirdupois is now defined as a unit of mass, (since 1959, apparently). The standard is actually based on the kilogram. |
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DannyUncanny wrote:Well like others said, one newton is equal to a kg meter per second squared. Seconds are defined by the frequency of cesium atoms. The kilogram is a kind of arbitrary mass roughly related to the density of water but actually defined by a platinum bar in Paris. The problem with that of course is that the bar is slowly losing mass. It's miniscule but still enough to be a worry for very precise physics.,The Pt bar is currently used as the standard for the SI kg, but a metric kg (which is equal in mass to the SI kg) was originally defined as the mass of 1 liter (1 dm^3) of water at 4 degrees C (the temperature at which water is most dense). A gram was originally defined by the mass of a cm^3 of water which is the same as a ml. Metric is pretty cool the way the units of mass, length and volume are all in terms of one another. Interestingly, the L is not an SI unit. In the American system of measurement there's a slight correlation between volume and weight. A fl oz of water weighs approximately one ounce, which puts a pint at about one lb. As to the issue of the Pt bar degrading over time, the CIPM is planning to redefine the kg in terms of the Planck constant. |
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The Bobby wrote: Now a harder question: where did pounds come from? :) What a stupid measurement. 1 lb = 6992 troy grains. WTF?Relic from England, which even England has gotten rid of, but the US is too conservative to give up. Kind of like how England abolished slavery a generation before we did. |
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muttonface wrote:You guys are some smart, fairly well educated sunzabitches.Engineering 101, actually high school physics 101, but I'd bet a shitload* of us are engineers or similar. (* shitload= 624896 x 10^-4) |
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It has always struck me as odd that the English system uses pounds as a weight (which is correct) but metric, which so wonderfully meshes together and is pretty much superior, uses a description of mass (kilograms) sometimes interchangeably with weight (newtons). |
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shuminW wrote:I think while the metric system is superior for scientific purposes, English system has advantage for everyday uses: what's 1/8 of a lb? 2 ounces. what's 1/8 of a kilograms? 125 grams. What's 1/3 of a foot? 4 inches. what's 1/3 of a meter? 33.3333.... centimeters??? Can you imagine using a decimal system for time in place of what we have now?Clearly this speaks to the advantages of the furlong-firkin-fortnight system of measurement. What's 1/11 of a furlong? 20 yards. What's 1/9 of a firkin? 10 lbs. What's 1/7 of a fortnight? 48 hours. Just try that with plain old feet, pounds or seconds. |
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Martin le Roux wrote: What's 1/9 of a firkin?I'm pretty sure that's 20 seconds. Oh wait, you wrote firkin? No idea what that is. |
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Mike Lane wrote: So if I jump up, I land with the force of 1 Kn? Or do I need to reach terminal velocity? Also, I'll bet the pound is something like the weight of a criminal's hand after being chopped off.Mostly depends what kind of shoes you are wearing. |
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I measure force in Chuck Norris units. |
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shuminW wrote: ...English system has advantage for everyday uses: what's 1/8 of a lb? 2 ounces. what's 1/8 of a kilograms? 125 grams. What's 1/3 of a foot? 4 inches. what's 1/3 of a meter? 33.3333.... centimeters??? Can you imagine using a decimal system for time in place of what we have now?I've been making this argument for years, but my geophysicist girlfriend and my engineer friends don't agree. The English system is based (within a unit anyway) on halves. Take a piece of paper and fold it in half. Easy, right? Now fold it into quarters. Also easy. Take another piece of paper and fold it into 10 equal sections. Wait, what? Also, for height: How tall are you? Six feet two. The feet unit gives a ballpark measure, the inches unit fine tunes it. How tall are you? One point eight eight meters (or one-hundred eighty-eight centimeters). You're forced to spit out all your precision at once. I also like the idea of using different units for different scales (in for small stuff, miles for big stuff). I can't quite explain why though. Now, for base ten calculations and unit conversions metric (sorry, it's SI now) is far superior. In reality I use both. If something's about a cm, I use cm, if it's about an inch I use inches. I shoot 9mm and .45acp. |
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interestingly enough a newton is approximately the weight of an apple, give or take. or so i've heard.... |