And if his, erm, boss had any anything to say about it, there'd have been ten commandments.
'Old on!
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There were 12 commandments but Moses forgot two of them on the way down Mouint Sinai.
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He may well have, but we haven't forgotten that this is not the silly thread ! :-)
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>>not the silly thread>>
No re Moses AND back to motoring, the bible says his Triumph was heard all over Israel ;-)
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No fast-fit exhaust centres in the desert, back then.
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And judging by the state of the walls of Jericho; his horn was illegally loud too!
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I somehow thought that would come up. He should have added a pint of oil to it !
Meanwhile.....
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Better think of a motoring link, for which tyres are a good example. The width is in millimetres (although the wheel width is in inches), the diameter (of the hole) is in inches, the load rating is in kg and the speed rating is in mph! You can however inflate it with psi, Pascals, bars, atmospheres or (my favourite) inches of mercury...
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JBJ
Can I be a pedant and mention that psi doesn't exist.
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"psi doesn't exist"
As in the paranormal? You may be right! The Greek letter and the pressure abbreviation do though, and the latter features prominently if you enter psi on its own into Google...
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JBJ
Told you I was being a pedant. Strictly speaking, the pound is a unit of weight; i.e. it requires a fixed amount of gravity to exist.
As - in this instance - air pressure is largely relative and mostly independent of gravity [and can even exist in deep space] the correct definition [all those Google references to psi pressures are wrong] is lbf/sq" - or pound FORCE per square inch.
I could get even more pedantic and drivel on about pressure/mass combinations; but that's enough for now.
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>>Strictly speaking, the pound is a unit of weight....
Don't you mean mass?
Number_Cruncher
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>>Strictly speaking the pound is a unit of weight.... Don't you mean mass?
Apparently it can be either (a force or a mass), at least according to the US. Goodness knows how that works -- it's in the scientific field where the Imperial measures become ever so slightly awkward -- constants everywhere to force-fit the system into standard equations.
Edited by Dynamic Dave on 10/03/2008 at 19:34
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>>(a force or a mass)...
Yes, usually when a force, called lbf, as per Screwloose's post, but when expressed as lb, it describes a mass.
I agree about Imperial measures being difficult to work with. In the past, when doing calcs for Boeing, I spend the first part of the calc converting everything into sensible units, I do the calc, evaluate a margin or reserve factor, and then, convert back into silly units for the US. For the calcs I do now, I would dream of using imperial measurements.
Having said all this, I'm perfectly happy with inches for timber, pints for beer, and miles for road journeys - I'd be happier with gallons than litres for fuel. Just not in a calc!
Number_Cruncher
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> Yes, usually when a force, called lbf, as per Screwloose's post, but when expressed as lb, it describes a mass.
Yeah, reading Screwloose's post again, I'd like to thank him for clearing that one up -- PSI never made much sense to me!
Coming from a scientific/engineering background (theoretical anyway -- my first degree was in Natural Sciences at Durham covering Maths, Physics and Computer Science), but having done little with all that knowledge in the engineering field since, I knew that pounds per square inch was wrong but couldn't quite put a finger on why exactly (not that I thought too much about it, or else I'd have quickly come up with the answer). Now I know -- it's pounds of force. D'oh!
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"convert back into silly units for the US"
This may be making a virtue of necessity, but that does at least provide a check that the numbers are sensible. Metrication makes it very easy to slip a decimal point - one reason I still do woodwork in feet and inches, although I tend to use mm for models.
There isn't really a problem except for the fundamentalists who want us all to conform to their idea of the world - which applies in a few other fields as well!
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Don't you mean mass?
I thought about which to use [not for long] and decided to sidestep the problem of "it's got mass but no weight" and keep it simple.
I also thus avoided the question of whether the pressure exerted at the top of an inflated tyre, stationary, upright, under normal gravity, was less than at the bottom.
I'll leave you to explore that one.....
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"less than at the bottom"
As we're measuring differential pressure (i.e above atmospheric) then the extra pressure at the bottom of the tyre (due to the weight of the air) will be exactly offset by the extra pressure outside, for the same reason. I think!
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JBJ
Ahh; but the air inside the tyre is denser as it's compressed....
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So if the valve is at the bottom and you measure the pressure then rotate the wheel through 180 deg and measure it again it will be different?
No, it will be the same, the tyre distorts at the bottom due to the weight applied to it though air displaced by this only serves to increase the pressure evenly within the tyre.
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So if the valve is at the bottom and you measure the pressure then rotate the wheel through 180 deg and measure it again it will be different?
Yes. Only marginally; gravity also acts on the denser air inside the tyre.
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"the air inside the tyre is denser"
So it is. Good job it gets mixed as you're going along!
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>>I also thus avoided...
Not really! - it's a question of physical reality rather than any choice of units to describe the problem.
Yes, there's an altitude dependent pressure gradient in the tyre (in any fluid come to that!), from top to bottom; delta_p = rho * g * delta_z
where rho is the density of the compressed air
g is the acceleration due to gravity
and delta_z is the change in height.
As a very rough off the top of head estimate, the pressure at the bottom is about 5 - 10 Pa greater than that at the top.
As the air is a fluid, the pressure is independent of the shape of the vessel.
Number_Cruncher
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NC
I know better than to argue with that......
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>> As a very rough off the top of head estimate the pressure at the bottom is about 5 - 10 Pa greater than that at the top.
.*********
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>> As a very rough off the top of head estimate the pressure at the bottom is about 5 - 10 Pa greater than that at the top.
So in technical terms then that is about half of sod-all!
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>>So in technical terms then...
Well, it depends why you are interested in the value. For most practical considerations, you're absolutely right, your life will probably not be changed one jot to know about the 10Pa difference.
As an example, for the instruments which I work on, low noise is an absolute priority, we worry about, and keep budgets over noise currents that designers of more industrial instruments (and home Hi-Fi for that matter) would consider completely irrelevant.
Number_Cruncher
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"it requires a fixed amount of gravity to exist."
But my pressure gauge, being made on Earth, already takes that into consideration! No reason why it would't work on the moon, though, as it is only measuring the differential. The pump bit wouldn't be so effective though...
(Which is, of course, why there are no pubs on the moon - no atmosphere.)
IGMC
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"Can I be a pedant and mention that psi doesn't exist"
Oh! I've just put 34 of them in each of my front tyres or was that just a lot of hot air?
--
e Prôf - Another Recycled Teenager
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>>although the wheel width is in inches>>
Anyway no point reinventing the wheel!
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Curious that inches for tyre diameters persist even on Le Congtinong. They're called pouces [thumbs] in French; don't know what the equivalents are in other languages.
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There are metric wheels, IIRC (late Citroen CX's?). Not sure they've caught on, though.
Are the Chinese fully metric? I imagine they had a home-grown measuring system at some point, and the US is a major customer...
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I'm happy with either, although find metric more logical.
milli=thousandth, centi=hundredth,kilo=thousand. Standard rules across the whole system.
A litre is a litre everywhere in the world. A gallon in the UK is not a gallon in the US.
But on the whole, I think there are far more important things to be concerned about as far as our great nation is concerned than this stupid obsession with one-upmanship with Brussels. Maybe we could start with looking at standards of living, healthcare, crime prevention, education and all the other things that survey after survey prove the Europeans do better than us. Or we could argue and waste energy on this nonsense for many years.
The whole debate and argument and the "metric martyrs" thing was pointless and irrelevant.
Cheers
DP
--
04 Grand Scenic 1.9 dCi Dynamique
00 Mondeo 1.8TD LX
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"pointless and irrelevant"
Not really. The EU commissioner was apparently impressed that the imposition of change showed his organisation in bad light, and removed the compulsion, thus saving this country a shed-load of money that would have been spent changing road signs and bottles and glasses in the old measures.
Money that can now be spent on healthcare, crime prevention, etc...
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My heart's agin the EU, yet no-one convincingly tells me what is wrong with western European countries.
Many of us seem happy to live there. Why not import their systems of law, measurement, government etc. Are ours really better than theirs?
However, no-one either tells me convincingly why we should be members [as opposed simply to free trade agreements].
Are the people of Nebraska worse off as part of a federation of states?
What I hate most is the shallow posturing by politicians, and the euqally shallow reporting by journalists - maybe we readers want no more than shallow?
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I don't particularly see the need for pounds, feet or inches (although it's easier to say 6" than 150mm as the number is smaller).
The one imperial unit the passing of which should be mourned is the currency. (I was born (shortly) after it was consigned to the history books.)
One third of a pound? That's 33 1/3p (better get out that .33333p piece) - or 6/8; so much easier.
Frankly, as looking after the pennies is no longer much point, the imperial currency would have eliminated itself by now anyway. All the coppers would have gone (recycled into plumbing!) and the shilling would still reign supreme - of which 20 to the pound.
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One third of a pound? That's 33 1/3p (better get out that .33333p piece) - or 6/8; so much easier.
The main advantage of imperial measurements over the base 10 metric system is that they can be divided into fractions much easier.
Fractions such as half, quarter, third, etc. are much easily comprehended in normal everyday use than the decimal equivalents, 0.5, 0.25, 0.333333333... "I'll have 0.3 of a Kilo of apples please."
I was brought up on metric measurements, yet still find feet, inches, miles and pounds much more natural to use when describing things. They're more 'human' based measures, based on human proportions; rather than those based on an incorrect calculation of the distance from the pole to the equator through paris.
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> The main advantage of imperial measurements over the base 10 metric system is that they can be divided into fractions much easier.
That depends on what sort of fractions you're talking about. 1.5th?
In any case, I'd be all for the imperial system if it were all based on powers of 2, but it isn't -- 1 pint=20 fluid ounces, 12 inches in a foot, 3(?) feet in a yard, 1760 yards in a mile, 14 pounds in a stone.
There is no consistency to the system.
If there were 8 or 16 inches say to the foot, 4 feet to the yard and so on, the system would be a lot more useable.
As it is, it relies far too much on memorising wildly varying multiples, and hence the comments about it dividing better don't really hold water.
In any case, a third of a pound? How does that divide into ounces? 5 1/3oz is hardly any easier than ~330g is it?
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(Imperial measurements) As it is it relies far too much on memorising wildly varying multiples
But there aren't very many, are there. Not exactly difficult.
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But there aren't very many are there. Not exactly difficult.
Hey, it's the metric bashers that keep bleating on and on about how hard decimal calculations apparently are, and how easy it is to divide imperial measures into fractions!!!
At the end of the day the ONLY reason you find imperial easier than metric is because it is what you are used to.
I learned both systems, understand them both equally well (and use them interchangeably on a day-to-day basis -- the number of times I've found myself referring to one item as "a metre long" and the next "a couple of inches longer than that"!!).
I have no particular problem with the imperial system, but even its most ardent fan must realise that it's a hodge-podge of ill-fitting measures with no inherent mathematical beauty about it. It's a mongrel, in effect. Metric on the other hand just works -- a litre of water is 10cm cubed, and weighs 1kg. Elegant in its simplicity -- each measure can be defined in simple decimal multiples of another.
Which is why the entire world, save a few silly backward countries, and the entire scientific community have gone metric. This is not some EU folly foisted on a proud sovereign nation as the Daily Mail would have you believe, it is simple common sense.
Or would you rather we went back to tanners and farthings as well?
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>> But there aren't very many are there. Not exactly difficult. Hey it's the metric bashers that keep bleating
I simply said that it is not very difficult to remember the "memorising wildly varying multiples" which you mentioned as a problem.
(bleatings snipped)
Metric on the other hand just works -- a litre of water is 10cm cubed and weighs 1kg. Elegant in its simplicity -- each measure can be defined in simple decimal multiples of another.
10cm is not a standard unit. A cubic metre is not 10L.
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10cm is not a standard unit. A cubic metre is not 10L.
Of course the cm is a standard unit, just as much as the foot is.
To put things another way, a cubic metre is 1000l. Care to give me the equivalent lb -> yard -> pint relationship?
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"I was brought up on metric measurements, yet still find feet, inches, miles and pounds much more natural to use when describing things."
Good man!
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They're called pouces [thumbs] in French; don't know what the equivalents are in other languages.
In Afrikaans, an inch is called a "duim" - a thumb. Same story!
--
e Prôf - Another Recycled Teenager
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I wish we could measure "time" as well in metric!
7 60 24 365 => cumbersome but we are so used to it!
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>time
Sure. Eight day week and two day weekend, anybody?
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Nah. How about five-day week and five-day weekend? Actually, I've got a feeling the Roman 'week' was something like a ten-day cycle; can anyone help me out with that?
While we're at it, let's go for a ten-month year. I propose February and November for the chop - miserable months!
Of course, the SI gets around the problem of multiples by not bothering with minutes, hours and so on - everything has to be in seconds.
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Time-wise the only fixed thing is 365.25 (ish). You could redefine your day into 10 long hours, and the hours int 100 minutes, and the minutes into 100 seconds. But you would STILL have to make an arbitrary election as to the number of weeks in the year/days in the week.
The Romans iirc had days of ten hours. Which represented daylight hours divided into ten. But I may be wrong
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"let's go for a ten-month year"
It's been tried (hence December) but didn't catch on...
I'm also finding it hard not be amused by this. Apparently the standard kilo isn't very standard after all:
www.theregister.co.uk/2007/09/13/kilo_loses_weight/
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>>I'm also finding it hard not be amused by this.
Well, I'm sure that if you've a better idea, the people at NPL and BIPM will be all too pleased to hear about it!
;-)
Number_Cruncher
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"if you've a better idea"
If it was the standard Pound, I'd give the matter some thought..
:-)
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"everything has to be in seconds"
A bit like measuring in millimetres, then!
We do have a decimal time system, of a sort, if you use a computer.
At the time of writing, the spreadsheet function =now() gives 39339.3969 which is really the number of days since the first of January 1900, with the 0.3969 representing the fraction of the day so far.
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>time Sure. Eight day week and two day weekend anybody?
10 hour working day and 4 day working week perhaps, though that is another argument.
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10 hour working day and 4 day working week perhaps though that is another argument.
Something with which I heartily concur and recommend having worked a four day week for the last 18 months, it is really very pleasant having the weekend commence at 17:00 on a Thursday!
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Back in the dark (both figuratively and literally) days of 1974, the industrial outfit I worked for changed the arrangements to three 12-hour days. The odd thing was that output was then better than it had been with five 8-hour days...
I don't know if others experienced the same, but the 3-day week was widely adopted for a while. I don't suppose BL production improved!
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>> 10 hour working day and 4 day working week perhaps though that is another argument.
Unlike me who is about to start a job with a 3-day, 5-hour working week :)
Still, at £45 an hour, I can afford to put my feet up lol.
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Bring back the pound, shilling and proper [d] pence, too. Enough of this funny decimal stuff! Foreign rubbish.
--
Roger. (Costa del Sol, España)
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Bring back the pound shilling and proper [d] pence too. Enough of this funny decimal stuff! Foreign rubbish. -- Roger. (Costa del Sol España)
I'm not sure what to make of this remark. Has to be a mickey-take -- someone professing to be living in Spain talking about foreign rubbish.
Anyone who has these kind of views had better be buying British (or British-made at a push) cars and other products wherever possible, or else they run the risk of being dismissed as hypocrites.
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