Talk:Pascal (unit)

This  level-4 vital article is rated C-class on Wikipedia's content assessment scale. It is of interest to the following WikiProjects:

‹See TfM› Physics High‑importance This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.PhysicsWikipedia:WikiProject PhysicsTemplate:WikiProject Physicsphysics articles High This article has been rated as High-importance on the project's importance scale.

This article states "one atmosphere is exactly equal to 1013.25 hPa.' This is the International Standard Atmosphere (ISA) which is used to calibrate instruments at certain temperatures and pressures. One Atmosphere is still 1000 hPa. --Metricmike (talk) 01:43, 9 April 2010 (UTC)[reply]

I don't think you'll find any authoritative sources saying that the atmosphere is [still] the same as the bar, though it's sometimes used with that meaning in informal contexts. Hqb (talk) 09:29, 9 April 2010 (UTC)[reply]

The article states "It is a measure of force per unit area i.e. equivalent to one newton per square meter or one joule per cubic meter.". A unit of force per unit area is not what's expressed as "one joule per cubic meter". A cubic meter is not an area. This should be cleared up. —Preceding unsigned comment added by 192.35.35.34 (talk) 19:59, 2 April 2009 (UTC)[reply]

Neither a joule is a newton, pressure is a force per unit area but also an energy density and a J/m^3=N*m/m^3. It's actually correct and worth stressing more. Think for example at the perfect gas law PV=NkT, p=NkT/V, an energy density. 79.21.143.99 (talk) 14:18, 16 April 2015 (UTC)[reply]

This artical say it is 1 kPa. The mars article says it is 0.1 kPa. One of these is wrong. My understanding is that it is 0.7-0.9 kPa which is just slightly above the point where water cannot exist in the liquid phase. Can those who made the wrong example make a correction? -- Terrell Larson

The Mars article (and other sources I checked) say it is typically 0.75 kPa. The 1 kPa order-of-magnitude figure that is given here seems to be a crude, but easy to memorize, valid, rounded version of that. Markus Kuhn 11:06, 30 Apr 2005 (UTC)

Blaise Pascal was an important mathematician, but Galileo Galilei was the first person to weigh the atmosphere. The unit of atmospheric pressure (perhaps) should be the Galileo, not the hectopascal. Pascal didn't do much in the area of weighing the atmosphere. Millibar is the best term, though. Trudy June 28th, 2005 11:03 Z

Is this a comment regarding the article? Markus Kuhn 17:00, 17 August 2005 (UTC)[reply]

I'm with Markus. But the comment makes for interesting and informative discussion, so I think it belongs here. --Orthografer 03:32, 20 October 2005 (UTC)[reply]

The problem, of course, is that the galileo is already a unit named after Galileo Galilei. Too bad for his fans that this non-SI unit has been thrown out with the advent of our modern International System, though we still see far too many vestiges of its use. It is a centimeter-gram-second unit of acceleration, something with which Galileo is much more associated than atmospheric pressure. Of course, the normal name is the shortened version gal; spelling it as galileo is extremely rare. It's weird for the Wikipedia article to be listed under that name. Gene Nygaard 03:43, 20 October 2005 (UTC)[reply]

c-g-s units are alive and well in the field of fluid dynamics; don't dismiss its use as vestigal. 81.103.21.179 (talk) 22:28, 12 February 2009 (UTC)[reply]

1 pascal (Pa) = 1 N/m² = 1 J/m³ = 1 kg·m^–1·s^–2
Are you sure that it's " 1 kg·m^–1·s^–2 " without such thing as an area? that's only Mass/Acceleration...

Mass/Acceleration would be " 1 kg·m^–1·s⁺² ". " 1 kg·m^–1·s^–2 " is Mass times Acceleration (" 1 kg·m·s^–2 "), divided by area (m²), hence one Pa. --agr 20:39, 25 April 2006 (UTC)[reply]

Sorry to be such a novice/unwitting terrorist, but I made a change to the page and didn't include links or anything like that. I added that the Pa is equal to one Joule/m^3 since I think that's important. I also apologize for sticking this comment here, but I didn't think it warranted a new section.

I wanted to know what a "pascal" was? So I came to wikipedia to find out. I read the write up on "pascal" and still do not know what a pascal is?

In order to completely understand what a "pascal" is, it is necessary to explain why Mr. Pascal first decided to use that unit of measurement. What reference point did he first use and why?

What is one pascal equal to in the physical universe?

Or how did he arrive at what we know as one "pascal"?

I expect it to be something simple.

Something that an elementary student could understand.

For example 0 degrees celcius is where water freezes and 100 degrees is where water boils. (Or in degrees kelvin, 0 is where everything freezes and stops.)

When those reference points are known then, degrees celcius (and kelvin) means something.

If it meant that one pascal was equal to the atmospheric pressure at sea level, then it would mean something.

That is simple. It is a reference point. It is something a person can wrap his mind around. It is an anchor point. Otherwise it is ambiguous.

Would someone who knows this stuff please include it in the write up on "pascal"?

1 Pa = The "pressure" exerted by a force of 1 Newton acting uniformly on an area of 1 sq. meter. That's what i learnt in School.

If you want a reference point,i'd say the example of Atmospheric pressure at sea level might not be the best example, but anyway atmos. Pressure is 101,325 Pascal at sea level, we approximate it to 100,000 for simple calculations.Daiyusha (talk) 09:26, 20 September 2016 (UTC)[reply]

Diogeneseii (talk) 21:41, 8 June 2014 (UTC) Diogeneseii[reply]

messurment: of compressed energy in meter cubic.

What???? Peter Horn 03:23, 1 September 2006 (UTC)

Perhaps that was a reference to the fact that pressure is measured in the same units as energy density, and that the two quantities are related. --Heron 20:34, 12 September 2006 (UTC)[reply]

Pascal is normally only meant to be used for pressure and stress (source: ISO 31-0, table 2), i.e. quantities that represent force per area. Markus Kuhn 21:01, 12 September 2006 (UTC)[reply]

Don't agree It's actually correct and worth stressing more. Think for example at the perfect gas law PV=NkT, p=NkT/V, an energy density. 79.21.143.99 (talk) 14:22, 16 April 2015 (UTC)[reply]

100 000 Pa devided by 101 325 Pa gives 750.062, not exactly 750 . Peter Horn 03:23, 1 September 2006 (UTC)

Uh? 100 000 Pa / 101 325 Pa = 0.9869232... 212.137.63.86 (talk) 11:54, 6 August 2008 (UTC)[reply]

Sorry I missed the discussion of the proposed move; I think it was a damn foolish idea.

But since it was moved, who is going to now step in and fix the 500 links to a disambiguation page at Pascal (click on What links here? for that page), and ensure that they go to the right article, rather than linking to a disambiguation page?

• Is it you, 71.4.99.4, the not only anonymous but unsigned proponent of this move? I'm going to hold you primarily responsible.
• Or is it you, GTBacchus, who actually made the move? I'm going to hold you responsible, too, since there is a high probablility of not getting the anonymous proponent to do so.
• How about Markus Kuhn, Salix alba, Beardo, Serge, Gazjo, and Duja? Do any of you intend to step in and help these editors out with this unaccomplished and necessary task?

Some things, such as redirects from ㎫, are no-brainers.

Whoever does it, once you get done, could you come back and tell us how many of those links went to the page that used to be there, and how many went somewhere else? That will give you a pretty good idea of how necessary that move was. Gene Nygaard 02:27, 19 September 2006 (UTC)[reply]

• The disambig argument is a good one, though I still would give support to the move, especially with the long term in mind (think 10 years). Can't a bot fix those links? Many of those links (50?) were to the wrong Pascal anyway but that's not relevant to this specific discussion (at least they're not 'wrong' now). For info: Blaise Pascal has about 400 links to it so it is just as a significant Pascal. Gazjo 05:22, 19 September 2006 (UTC)[reply]
• :Heck, if we're counting links, one of the redirect pages to Pascal (programming language) alone has over 600. -GTBacchus^(talk) 04:37, 20 September 2006 (UTC)[reply]

Sure, I'll work on some of those. I don't see it as an big deal though; they'll get sorted out. Like Gazjo said, the pages are in the right place now, and the links will be fine, in some time. I'll do a few a day, and chip away at it. As far as getting an idea of "how necessary the move was", that sounds a bit fatuous, doesn't it? I just picked out 10 links, eight of which wanted to point to the unit, one to the programming language, and one to the philosopher. I'd rather a Blaise Pascal link point to a disambiguation page than a page about pressure measurement. -GTBacchus^(talk) 08:49, 19 September 2006 (UTC)[reply]

It's under 400 now. I got most of the ones that were for the programming language, I think. More later. -GTBacchus^(talk) 09:27, 19 September 2006 (UTC)[reply]

Most of the links that need fixing should actually have been to kPa, MPa, GPa, etc. and should have been fixed anyway. The list of pages that need fixing is getting smaller rapidly. Number of links is not a good measure of the dominant meaning of a term, especially for a unit of measure, which attracts a lot of links merely for technical reasons. The decision to move was certainly correct IMHO. Markus Kuhn 12:23, 19 September 2006 (UTC)[reply]

All of those pages like kPa redirect to Pascal (unit) now. During the move, I went ahead and snapped all the double redirects. Most of the incoming links seem to be of the form [[Pascal|kPa]] or something, so fixing the redirects didn't help them. -GTBacchus^(talk) 18:14, 19 September 2006 (UTC)[reply]

Down to 300 -GTBacchus^(talk) 04:34, 20 September 2006 (UTC)[reply]

200... -GTBacchus^(talk) 03:28, 27 September 2006 (UTC)[reply]

All main article name space links done. --Salix alba (talk) 14:59, 29 September 2006 (UTC)[reply]

One hectopascal corresponds to about 1% of atmospheric pressure (near sea level)..."

Is this right? According to Pascal (unit), "the average atmospheric pressure, at sea level, is about 101.3 kilopascals", and since one hectopascal is 10 times less than a kilopascal, one hectopascal should be 0.1% of atmospheric pressure, shouldn't it? Palefire 07:58, 17 January 2007 (UTC)[reply]

In the article it says that 1 atm= 101 325. WTF is that? Is that 101 and 325? 101,325? What? WHO THE HELL WROTE THAT? —Preceding unsigned comment added by Paladin Hammer (talk • contribs) 01:19, 22 October 2007 (UTC)[reply]

It's a common notation that is a compromise for displaying high precision numbers, but MOS:NUM says we don't use it on Wikipedia, so I have changed it in the article.--agr 15:30, 22 October 2007 (UTC)[reply]

Various international standards (e.g., ISO 31-0) recommend that long numbers are split into groups of three digits, separated by a thin space, whereas the housestyle of the English-language Wikipedia requires to separate such groups of three digits with a comma. (The latter approach does not work in many other European languages, where a decimal comma is used.) It is pretty much the only area where the English Wikipedia MoS disagrees with international standards, but because many web browsers and keyboards still do not support a thin-space character (and NBSP is awkward to enter), the traditional English-style comma group separator has won. Markus Kuhn 08:14, 24 October 2007 (UTC)[reply]

May I propose that the conversion table be written in scientific notation? Those commas and dots are not easily discernible (apart from being non standard across countries), for instance the atm to Pa conversion could be: 1 atm = 1.01325 10⁵ Pa. HumphUK (talk) 10:01, 13 February 2009 (UTC)[reply]

Just to add confusion to the mix, someone used a period as the decimal group separator in one place in the article. I just fixed that, but in the edit summary comment I said "decimal mark" when I meant "group separator". Ah well... --24.131.145.233 (talk) 23:41, 21 February 2015 (UTC)[reply]

According to WP:DIGITS: In scientific/engineering articles, long strings left of the point may be grouped into triples without commas. In such case we can use the Wikipedia template {{val}}: {{val|101325}} → 101325. Try to select this value with mouse, and you will see no space character between 2 groups of digits, as well as no ambiguous separator. Could this format be more reasonable? --37.190.52.185 (talk) 18:10, 21 March 2015 (UTC)[reply]

Yes, this particular value is a magnet for trouble. Use a comma and someone who reads that as a decimal separator will "correct" the unit to kPa. Following your suggestion, by going a step further using {{convert}} to give "101325 Pa (101.325 kPa)" we can have a non-breaking space and an explicit conversion to kPa, plus {{convert|101325|Pa|kPa|abbr=on|comma=gaps}} may be a bit more daunting to edit! I'll try it. NebY (talk) 10:26, 22 March 2015 (UTC)[reply]

It is my understanding that 101.364KPa is the same as 1 Atm,but the article states that it is 101.325Kpa,which is a big difference when doing a lengthy calculation and you need the unit as close to the decimal as possible. —Preceding unsigned comment added by 206.255.88.85 (talk) 22:53, 20 March 2008 (UTC)[reply]

I've never seen 1 atm defined as 101.364 kPa; can you point to a reliable source for that number? Hqb (talk) 17:57, 30 March 2009 (UTC)[reply]

Redirect to the orders of magnitude page, OR , merge the magnitude page in please! I'm not much of an editor, so you get to decide. found it on google though :) (I marked out my own comment below)

I was doing a search for a term that I couldn't find even on google, GPa, and it redirected here, but using the browser's search tool to find it on the page yeilded only one result, the redirection notice.

Please fix this soon, someone, anyone? —Preceding unsigned comment added by 24.22.176.33 (talk) 01:58, 23 April 2008 (UTC)[reply]

how much is 15 PAmin in L.s Is it 15 L.s of 900 L.s —Preceding unsigned comment added by 196.35.246.194 (talk) 13:19, 8 June 2008 (UTC)  Not done Question Unclear[reply]

1atm = 1.01 x 10⁵Pa = 13534[kgm^-3] x 9.81[Nkg^-1] x 0.76[m] where 13534kgm^-3 is the density of liquid mercury, 9.81Nkg^-1 is the gravity constant, 0.76m is the height of mercury in a mercury-in-bulb thermometer.

This derivation is based on several inaccurate assumptions. Have a look at Torr#Manometric units of pressure. Hqb (talk) 18:30, 24 September 2009 (UTC)[reply]

GPa is used not only by Tectonophysicists, but also (and I guess this use is much more substantial) in Mechanical Engineering, see [1], quote:

...Young's modulus is the ratio of stress, which has units of pressure, to strain, which is dimensionless; therefore Young's modulus itself has units of pressure.

The SI unit of modulus of elasticity (E, or less commonly Y) is the pascal (Pa or N/m²); the practical units are megapascals (MPa or N/mm²) or gigapascals (GPa or kN/mm²). —Preceding unsigned comment added by 77.126.173.47 (talk) 16:45, 11 February 2010 (UTC)[reply]

Well, as there was no opposition, I added this myself (my first wikipedia edit :) ... —Preceding unsigned comment added by 89.138.141.137 (talk) 19:29, 14 November 2010 (UTC)[reply]

In the top right box on this page, it says kg/m^2, which doesn't make much sense... I'm almost 100% sure it's newtons/m^2 —Preceding unsigned comment added by 98.185.253.215 (talk) 17:53, 11 April 2010 (UTC)[reply]

It actually says "kg / (m·s^2)". I.e., the denominator is "metres times seconds squared", not "metres squared". N / m^2 is also correct, and makes immediate physical sense, but the newton is not an SI base unit. Hqb (talk) 18:36, 11 April 2010 (UTC)[reply]

It all comes down to mass,distance and time units - the ones independent of other units. That's how the SI system is derived, all physical quantities are derived from these and 3 more(Temperature,Luminance,current). you may include the Chemistry's mole_(unit) too. Any other quantities are just comprised of these above 7.

Just some questions regarding pascals in different numbers of dimensions.

For instance, would a "2D pascal" be the same as a force of one newton being applied over one metre (not a joule, but a newton is "spread" over a metre, like a pascal is a newton "spread" over a square metre)? What about a "4D pascal"? Would it be the same as one newton acting over 1 cubic metre? Could somebody please clarify this for me? —Preceding unsigned comment added by 75.104.128.36 (talk) 18:14, 19 April 2011 (UTC)[reply]

Nope that's not how pressure works, pressure acts on a 2D surface(measured in sq metres), if any other force is acting as per your 2D pascal definition(and as a matter of fact it doesn't), that would be a separate unit and IS NOT PASCAL. Pressure is Force per unit area period, there is nothing called 2D pascal and if there is, its not related to Pascal now.

In the definition of Pascal as a force of 1 N acting over a sq meter, imagine this: A 1m x 1m patch on the ground. Now that patch is filled with points right. Let us imagine forces acting on each of these points.(Force acts on a point as per definition). If the total of all the forces acting perpendicularly on each of the points in the patch is 1N, then the pressure is 1N/(1m*1m) = 1 Pa.

Now regarding the force over a single meter, No matter how small the line may be, if there exists a point, the line also has a infinitesimal(infinitely small, but >0) area. And the force will now be acting over an area and will be calculated as pressure.Daiyusha (talk) 09:44, 20 September 2016 (UTC)[reply]

This comment was moved from elsewhere on this talk page by User:Martinvl

There is an inconsistent use of capitalization of letters according to the SI rules... That is that if the unit with the pronoun, such as kilo, is larger than the unit, Pascal for example, then the letter should be capitalized, therefore KPa rather than kPa and HPa rather than hPa. Sorry if this is in the wrong area but I did not know where else to comment. David Marshall B.Ed. (talk) 08:35, 3 July 2011 (UTC)[reply]

The definive statement of the SI system states lists prefixed for 10⁶ and greater are upper-case (M, G, T etc), others are lower-case.

See International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), ISBN 92-822-2213-6, archived (PDF) from the original on 2021-06-04, retrieved 2021-12-16

Martinvl (talk) 09:07, 3 July 2011 (UTC)[reply]

Suggest we restore Sixty Symbols video as quite relevant. Moriarty is a full Professor of physics at UofN [2]; video illustrates pascales, etc quite nicely. – S. Rich (talk) 20:37, 30 April 2013 (UTC)[reply]

1 Pa = 1 kg/(m·s2)--Wyn.junior (talk) 00:29, 6 April 2014 (UTC)[reply]

That would be the metre, the SI base unit of length, as also noted in the body of the article. Hqb (talk) 06:03, 6 April 2014 (UTC)[reply]

What is the significance of the "·" in "1 Pa = 1 kg/(m·s2)"?--Wyn.junior (talk) 23:52, 6 April 2014 (UTC)[reply]

That's a multiplication dot, necessary to avoid confusion between "ms²" (milliseconds squared) and "m·s²" (metres times seconds squared). The form "m s²" (with a non-breaking space!) is also allowed by the SI rules, but runs a higher risk of misinterpretation, so is generally better avoided. Hqb (talk) 08:00, 7 April 2014 (UTC)[reply]

I linked the "/" and "·" so readers know what those are.--Wyn.junior (talk) 14:28, 7 April 2014 (UTC)[reply]

What is the full way to say "s2" in "1 Pa = 1 kg/(m·s2)"? I'd like the link the full version of that also if possible.--Wyn.junior (talk) 23:52, 6 April 2014 (UTC)[reply]

I can't tell what you are asking. Unlike "m²" (square metre, the SI unit of area), the unit "s²" (square second?) has no natural physical interpretation, and is almost never used by itself. Hqb (talk) 08:00, 7 April 2014 (UTC)[reply]

What is a second squared? "Second squared" and "square second" do not have articles on Wikipedia. Is it simply a second?--Wyn.junior (talk) 14:28, 7 April 2014 (UTC)[reply]

It comes from the definitions what a Newton [N] is (see here) as the N in the first formula was replaced by its definition in S.I. basic units, that N becomes m*kg per square-second. The square-second in this expression comes from acceleration (we all learned very well what acceleration is: the gradient of speed . And as a derivate is based on dt, one must devide with second, so you become second * second = square-second. This is tuff is college schoolars daily bred.--Cosy-ch (talk) 07:14, 22 May 2015 (UTC)[reply]

This sentence is completly wrong: "Standard atmospheric pressure is 100 kPa.[6] This definition is used for pneumatic fluid power (ISO R554), and in the aerospace (ISO 2533) and petroleum (ISO 5024) industries."

All kind of calculations in the gas industry worldwide (exept in USA) are based on Standard atmohsphere (1013.25 hPa). The normilzed cubic meter of natural gas for example , as well as the formulas for the ideal and real gas physics are based on that same number. Borkers refers worldwide to quantities based on this standard pressure (as well as the standard temperature).

Pneumatics- at least in europe, is in the absolute pressure range also refered to the standard athmosphere. At least it is so in Europe.

The standard in aviation is still and will be kept at 1013.25 hPa. (By the way, the hecto is written in minor and not in capital letters- see ISO and System definitions for SI) --Cosy-ch (talk) _Standard_in_Aeronautics" class="ext-discussiontools-init-timestamplink">07:03, 22 May 2015 (UTC)[reply]

Yes. I've tried to repair and clarify it, and tried to explain the difference between reference conditions and unit of measurement further at Talk:Atmosphere (unit)#IUPAC, atm and standard pressure. I think the capitalisation is correct now - hPa and hectopascal, except where a section heading begins with a capital H in the unit name. NebY (talk) 22:03, 22 May 2015 (UTC)[reply]

Hello fellow Wikipedians,

I have just modified one external link on Pascal (unit). Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20070618123613/http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html to http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 18:15, 21 May 2017 (UTC)[reply]

Hello fellow Wikipedians,

I have just modified 3 external links on Pascal (unit). Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20070630020548/http://www.bipm.fr/en/convention/cgpm/14/pascal-siemens.html to http://www.bipm.fr/en/convention/cgpm/14/pascal-siemens.html
• Added {{dead link}} tag to http://www.dwd.de/de/WundK/W_aktuell/Beobachtungen.htm
• Added archive https://web.archive.org/web/20060506192242/http://www.meteoam.it/modules.php?name=analisiPrevisioniSuolo to http://www.meteoam.it/modules.php?name=analisiPrevisioniSuolo
• Added archive https://web.archive.org/web/20110604131321/http://www.ctv.ca/servlet/HTMLTemplate/!ctvDynNews/Weather/Weather?City=Montreal to http://www.ctv.ca/servlet/HTMLTemplate/!ctvDynNews/Weather/Weather?City=Montreal

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 07:57, 6 December 2017 (UTC)[reply]