Date: 6 Oct 2004 05:17:53 -0700 From: gnygaardnospamay.com (Gene Nygaard) Subject: Re: Town And Country Miles
Malcolm William Mason <mwm1(delete)nospamedu> wrote in message news:<ai57m0hbvf9238qh72j42jntbvo9od2vugnospamcom>... > On Sat, 02 Oct 2004 18:24:13 GMT, amesnospamrak.demon.co.uk (Andrew > Stephenson) wrote: > > >In article <3rdsl01oll2tuc3mm5pnaup4f05v0l98finospamcom> > > mwm1(delete)nospamedu "delete" writes: > > > >> And, I am almost too embarrassed to ask but exactly what is a > >> Newton in kilos or grams. [...] > > > >Not trying to tread on the other response, which gives numbers... > > > >IIRC, "newtons" often cause confusion in modern physics classes. > >Formally, the SI unit "newton" is that force which, acting on a > >mass of one kilogramme, causes it to accelerate by 1 metre/sec^2. > > > >Thus a lump of 1 kilo _mass_ (NB) on Earth exerts a _force_ (NB) > >downward due to Earth's gravity of roughly 9.807 newtons. > > > IIRC, "newtons" often cause confusion in modern physics classes. > Formally, the SI unit "newton" is that force which, acting on a > mass of one kilogramme, causes it to accelerate by 1 metre/sec^2. > > Just like a good old dyne only very much bigger. one dyne accelerates > one gram one cm. per secnd per second. > And that is from a loooooong time ago! > > Thus a lump of 1 kilo _mass_ (NB) on Earth exerts a _force_ (NB) > downward due to Earth's gravity of roughly 9.807 newtons. > > But weighs one kilo (kilogram) correct? THe use of "kilo" for kilogram is certainly not correct. The use of kilograms for weight is correct. However, many people get confused, mistakenly thinking that this means that those kilograms are thus units of force rather than units of mass. Weight is an ambiguous word, one with several different meanings. But its usage in commerce, for example, is much more uniform and consistent than its usage in the various sciences. Yet it is hard to believe how many people are so confused that they think that when we buy and sell goods by weight, we'd want to measure some quantity which varies with the strength of the gravitational field. We should not do so; we do not do so; we have never done so. The use of kilograms force is no longer correct. > And is Newton not capitalized as in Sir Isaac? No. Not in English. Nor are the watts, amperes, volts, joules, kelvins, and the like. > Physicists and designers of machinery prefer to be very careful > when saying words such as "kilo", "newton", "mass" and "force". > > And weight.? The best thing to do is to avoid that ambiguous word in a technical context. > Blokes heaving on spanners here on Earth can get by with saying > that 1 newton of force == 1 kilo of force. > > > > Malcolm Mason Certainly not. Yes, there is a kilogram force--by definition, exactly 9.80665 newtons. So 1 newton is approximately 100 grams force. But that kilogram force should no longer be used. It is not a part of the modern metric system, the International System of Units. -- Gene Nygaard http://ourworld.compuserve.com/homepages/Gene_Nygaard/ "It's not the things you don't know what gets you into trouble. "It's the things you do know that just ain't so." Will Rogers
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