im钱包下载官网安卓版|preassure
作者： im钱包下载官网安卓版
2024-03-13 04:21:30
Pressure Definition & Meaning - Merriam-Webster
Pressure Definition & Meaning - Merriam-Webster
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Est. 1828
Dictionary
Definition
noun
verb
noun
2
noun
verb
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pressure
1 of 2
noun
pres·sure
ˈpre-shər
Synonyms of pressure
1
a
: the burden of physical or mental distress
b
: the constraint of circumstance : the weight of social or economic imposition
2
: the application of force to something by something else in direct contact with it : compression
3
archaic
: impression, stamp
4
a
: the action of a force against an opposing force
b
: the force or thrust exerted over a surface divided by its area
c
: electromotive force
5
: the stress or urgency of matters demanding attention : exigency
people who work well under pressure
6
: the force of selection that results from one or more agents and tends to reduce a population of organisms
population pressure predation pressure
7
: the pressure exerted in every direction by the weight of the atmosphere
8
: a sensation aroused by moderate compression of a body part or surface
pressureless
adjective
pressure
2 of 2
verb
pressured; pressuring
ˈpre-sh(ə-)riŋ
transitive verb
1
: to apply pressure to
2
: pressurize
3
: to cook in a pressure cooker
Synonyms
Noun
strain
stress
tension
Verb
blackjack
coerce
compel
constrain
dragoon
drive
force
impel
impress
make
muscle
obligate
oblige
press
sandbag
See all Synonyms & Antonyms in Thesaurus
Examples of pressure in a Sentence
Noun
Apply pressure to the wound to stop the bleeding.
the pressure of the compressed air inside the chamber
The animal's jaws can exert a pressure of more than 750 pounds per square inch.
The horse will respond to the slightest pressure of a rider's knee.
The fruit yields to gentle pressure when it's ripe.
the normal air pressure at sea level
He gave in to the social pressures to act and dress like everybody else.
She felt a constant pressure to earn more money.
Verb
his father pressured him to go out for the swim team
See More
Recent Examples on the WebNoun
These offerings are designed to alleviate staffing pressures and improve patient flow through smart, flexible partnerships with hospitals and health systems responding to clinical workforce shortages.
—Sacramento Bee, 5 Mar. 2024
Doing that puts a lot of pressure on the rest of this K-State team that can struggle to score overall.
—Shreyas Laddha, Kansas City Star, 5 Mar. 2024
Their plans kept changing (the bride was under a bit of pressure from her future mother-in-law), and the wedding was eventually held at a larger venue with 50 guests from both sides of the family, many of whom traveled to be there.
—Jacobina Martin, Washington Post, 4 Mar. 2024
These include studying the effects of microgravity and UV radiation on plants, using stem cells to create models to study degenerative disease and testing whether wearing pressure cuffs on the legs could prevent fluid shifts and reduce health problems in astronauts.
—Russell Lewis, NPR, 4 Mar. 2024
Keep in mind that Williams yielded just one sack and six pressures in 280 pass blocking snaps over nine games.
—Barry Jackson, Miami Herald, 4 Mar. 2024
Historically found on Indiana’s prairie lands thanks to pressure from wolves, coyotes expanded their range after European colonizers killed all of Indiana’s wolf populations in the early 1900s.
—Karl Schneider, The Indianapolis Star, 4 Mar. 2024
By that time, all independent media was coming under increasing pressure as Hun and his Cambodia People's Party tightened their grip on power and sought to silence most critics.
—Sopheng Cheang The Associated Press, arkansasonline.com, 3 Mar. 2024
The team’s inability to get anything at all going in the rushing game put way too much pressure on quarterback Baker Mayfield, which in turn stressed the Tampa Bay offense beyond repair.
—Lorenzo Reyes, USA TODAY, 23 Feb. 2024
Verb
The stock was further pressured Friday after Fitch Ratings downgraded NYCB’s debt to junk status and Moody’s Investors Service lowered its rating further into junk territory.
—Nicole Goodkind, CNN, 6 Mar. 2024
Perhaps, without a war to rally the faithful, the Houthis could be pressured toward compromise and consensus.
—Robert F. Worth, The Atlantic, 5 Mar. 2024
After being hailed for revolutionizing television and pumping out content as if there was no tomorrow, streaming sites also are losing subscribers and being pressured by Wall Street to turn a profit as soon as possible, not somewhere down the road.
—Julie Hinds, Detroit Free Press, 4 Mar. 2024
Institutional investors are pressuring Japanese companies to add more women to their boards.
—Emma Hinchliffe, Fortune, 4 Mar. 2024
This success has pressured competitors like Meta Platforms and Samsung, a long-time rival of Apple in various product categories.
—Charlie Fink, Forbes, 1 Mar. 2024
Authorities had pressured the family to avoid a public funeral, according to his mother.
—Francesca
ebel, Washington Post, 1 Mar. 2024
This is the result of a campaign led by Arab-American activists to use the ballot box to pressure Biden to call for a cease-fire in Gaza.
—USA TODAY, 28 Feb. 2024
And an intense lobbying effort by the Air Force and major arms contractors designed to pressure his administration into building a costly new nuclear bomber was one of the primary reasons that President Dwight D. Eisenhower warned of the dangers of the military-industrial complex.
—William Hartung, Forbes, 22 Feb. 2024
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These examples are programmatically compiled from various online sources to illustrate current usage of the word 'pressure.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Word History
Etymology
Noun
Middle English, from Anglo-French, from Late Latin pressura, from Latin, action of pressing, pressure, from pressus, past participle of premere
First Known Use
Noun
14th century, in the meaning defined at sense 1a Verb
1938, in the meaning defined at sense 1
Time Traveler
The first known use of pressure was
in the 14th century
See more words from the same century
Phrases Containing pressure
bilevel positive airway pressure
pressure cabin
pressure group
low blood pressure
vapor pressure
pressure cooker
sound pressure
partial pressure
pressure suit
counter-pressure
tire pressure
barometric pressure
continuous positive airway pressure
root pressure
pressure wave
low-pressure
pressure point
high blood pressure
blood pressure
take the pressure off
under pressure
predation pressure
peer pressure
pressure gauge
osmotic pressure
water pressure
high-pressure
See More
Dictionary Entries Near pressure
pressural
pressure
pressure accumulator
See More Nearby Entries
Cite this Entry
Style
MLA
Chicago
APA
Merriam-Webster
“Pressure.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pressure. Accessed 12 Mar. 2024.
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Kids Definition
pressure
1 of 2
noun
pres·sure
ˈpresh-ər
1
: a force or influence that cannot be avoided
social pressure
2
: the application of force to something by something else in direct contact with it
keep steady pressure on the gas pedal
3
a
: the action of a force against an opposing force
b
: the force applied over a surface divided by its area
c
: the force exerted as a result of the weight of the atmosphere
4
: the stress or burden of matters demanding attention
works well under pressure
pressure
2 of 2
verb
pressured; pressuring
ˈpresh-(ə-)riŋ
1
: to apply pressure to
2
: pressurize
Medical Definition
pressure
noun
pres·sure
ˈpresh-ər
1
: the burden of mental or physical distress especially from grief, illness, or adversity
2
: the application of force to something by something else in direct contact with it : compression
3
a
: the action of a force against some opposing force : a force in the nature of a thrust distributed over a surface
b
: the force or thrust exerted over a surface divided by the area of the surface
4
: electromotive force
5
: atmospheric pressure
6
: a touch sensation aroused by moderate compression of the skin
More from Merriam-Webster on pressure
Nglish: Translation of pressure for Spanish Speakers
Britannica English: Translation of pressure for Arabic Speakers
Britannica.com: Encyclopedia article about pressure
Last Updated:
8 Mar 2024
- Updated example sentences
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PRESSURE | English meaning - Cambridge Dictionary
PRESSURE | English meaning - Cambridge Dictionary
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English (UK)
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English
Meaning of pressure in English
pressurenoun uk
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/ˈpreʃ.ər/ us
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/ˈpreʃ.ɚ/
pressure noun
(PUSHING)
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C2 [ U ] the force you produce when you press something: He put too much pressure on the door handle and it snapped. You can stop bleeding by applying pressure close to the injured area.
C1 [ C or U ] the force that a liquid or gas produces when it presses against an area: gas/water pressure The new material allows the company to make gas pipes which withstand higher pressures. The gas is stored under pressure (= in a container which keeps it at a higher pressure than it would usually have).
More examplesFewer examplesIf you apply pressure to a cut it's meant to stop the bleeding.She tried to cure the pain in my knee by putting manual pressure on the joint.The alarm is activated by the lightest pressure.My ankle is extremely painful if I put any pressure on it.The vacuum inside the tube caused it to implode when the external air pressure was increased.
SMART Vocabulary: related words and phrases
Physics: energy, force & power
animal magnetism
anti-gravity
attract
attraction
ballistic
entropically
equilibrant
erg
excited
frictional
geothermal
inertia
jet propulsion
propulsive
radiant energy
self-propulsion
sine curve
sinusoid
the sound barrier
thermodynamics
See more results »
pressure noun
(PERSUADING)
B2 the act of trying to make someone else do something by arguing, persuading, etc.: public/political pressure Teachers are under increasing pressure to work longer hours. [ + to infinitive ] Pressure to abandon the new motorway is increasing. The government is facing pressure from environmental activists. The Defence Secretary resigned under pressure from the Prime Minister (= because the Prime Ministerforced him to). She's putting pressure on him (= trying to persuade him) to get married.formal The international community is trying to bring pressure to bear on the government (= trying to persuade them) to resolve the situation.
B2 [ C or U ] a difficult situation that makes you feel worried or unhappy: She's got a lot of pressure on her at work just now. Be nice to him - he's been under a lot of pressure recently. Can you work well under pressure? the pressures of work
so no pressure then! humorous
something that you say when what someone has just said makes you feel that you must try very hard to do something: "These exams are the most important of all." "Oh, so no pressure then!"
[ U ] a situation in a football game in which attacking players are moving forward and getting closer to scoring a goal, and players from the opposing team have to work hard to stop them from scoring: Ryan Giggs put the home defence under pressure. Playing four forwards puts too much pressure on the defence.
More examplesFewer examplesThey are putting pressure on the government to equalize state pension ages between men and women.Some managers exert considerable pressure on their staff to work extra hours without being paid.He's putting pressure on me to change my mind.Despite renewed pressure to give up the occupied territory, they will not yield.Her confession could not be admitted as evidence because it was given under pressure from the police.
SMART Vocabulary: related words and phrases
Causing somebody to act
arm-twisting
bludgeon
bounce someone into something
browbeat someone into something/doing something
bull something through
coercion
dragoon someone into something
duress
force someone's hand idiom
forced marriage
forcible
push (someone) toward(s) something
put the heat on someone idiom
put/tighten the screws on someone idiom
rallying cry
ram something down someone's throat idiom
ransom
slap
squeeze
wring
See more results »
You can also find related words, phrases, and synonyms in the topics:
Urging & persuading
Anxiety and worry - general words
Trying and making an effort
Competing in sport
Football/soccer
pressureverb [ T ] US uk
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/ˈpreʃ.ər/ us
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/ˈpreʃ.ɚ/ (UK pressurize)
to strongly persuade someone to do something they do not want to do: She was pressured into joining the club. Synonym
coerce formal
SMART Vocabulary: related words and phrases
Causing somebody to act
arm-twisting
bludgeon
bounce someone into something
browbeat someone into something/doing something
bull something through
coercion
dragoon someone into something
duress
force someone's hand idiom
forced marriage
forcible
push (someone) toward(s) something
put the heat on someone idiom
put/tighten the screws on someone idiom
rallying cry
ram something down someone's throat idiom
ransom
slap
squeeze
wring
See more results »
You can also find related words, phrases, and synonyms in the topics:
Urging & persuading
(Definition of pressure from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
pressure | American Dictionary
pressurenoun us
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/ˈpreʃ·ər/
pressure noun
(FORCE)
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Add to word list
[ C/U ] the force produced by pressing against something: [ U ] air/blood/water pressure
[ C/U ]
physics Pressure is also the force that is put on a surface with reference to the area of the surface.
pressure noun
(INFLUENCE)
[ C/U ] a strong, often threatening influence on an organization or person: [ C ] Competitive pressures will force the company to sell off its factories.
[ C/U ] If you put pressure on someone, you try to cause that person to do something by persuading or threatening them: [ U ] They put a lot of pressure on him to resign.
pressure noun
(WORRY)
[ U ] worry and fear caused by the feeling that you have too many responsibilities and cares: I like this job – there’s not so much pressure to produce every day.
pressure verb [ T ] us
Your browser doesn't support HTML5 audio
/ˈpreʃ·ər/
She was pressured into signing the agreement.
(Definition of pressure from the Cambridge Academic Content Dictionary © Cambridge University Press)
pressure | Business English
pressurenoun [ C or U ] uk
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/ˈpreʃər/ us
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Add to word list
Add to word list
a situation in which someone tries to make someone else do something by arguing, persuading, etc.: public/political pressure The guidelines were imposed under pressure from Congress.
a difficult situation, or the worried feeling that such a situation can give you: pressure on sb She's got a lot of pressure on her at work just now. He doesn't work well under pressure. The pressures of work are making her depressed.
put pressure on sb/sth
to put someone or something in a difficult situation, or to try and persuade or force someone to do something: Analysts said the lack of supply would undoubtedly put pressure on prices.
(Definition of pressure from the Cambridge Business English Dictionary © Cambridge University Press)
Examples of pressure
pressure
Initially, as the plasma plume is formed, the particle pressure is very high due to high value of pressure and density.
From the Cambridge English Corpus
Since the key issue is the psychological pressure that law can exert on every individual mind, the law must be clear, well diffused, and foreseeable.
From the Cambridge English Corpus
For instance, over-blowing on a wind instrument can cause an octave rise, which holds as the pressure is reduced.
From the Cambridge English Corpus
The duct was then replaced and the oscillating pressure measured in similar conditions.
From the Cambridge English Corpus
The surprising behaviour of the surfaces of constant total pressure occurs entirely in the boundary layer.
From the Cambridge English Corpus
This residue in its turn is then subjected to distillation under reduced pressure to give both a vacuum distillate and a vacuum residue.
From the Cambridge English Corpus
Possibly, this urban market absorbed part of the area's rural workforce, thereby lightening the pressure on those who sought access to arable land.
From the Cambridge English Corpus
High pressure studies of energy transfer and strongly coupled bacteriochlorophyll dimers in photosynthetic protein complexes.
From the Cambridge English Corpus
The right ventricular systolic pressure tends to decrease with age.
From the Cambridge English Corpus
Thus, each year the worms were subjected to selection pressure during 2 steps, and to genetic drift during 22 steps.
From the Cambridge English Corpus
Following a pressure increase in the pipette, the cell suspension was transferred to seminiferous tubules (dark blue).
From the Cambridge English Corpus
The turbulence energy balance is examined, including the separate effects of vertical diffusion of pressure and local kinetic energy.
From the Cambridge English Corpus
However, escalating divergence of the populations is unlikely in the presence of gene flow unless they experience persistently different selection pressures.
From the Cambridge English Corpus
The vertical structure of both the wind velocity and pressure fields shows interesting variation along the wave profile.
From the Cambridge English Corpus
The basic uncertainty in pressure readings was estimated t o be 0.003 vertical inches of water.
From the Cambridge English Corpus
See all examples of pressure
These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors.
Collocations with pressure
pressure
These are words often used in combination with pressure.Click on a collocation to see more examples of it.
added pressureThat would have been an added pressure to make sales.
From the Hansard archive
Example from the Hansard archive. Contains Parliamentary information licensed under the Open Parliament Licence v3.0
ambient pressureThe results show that the ambient pressure has an important effect on the properties of plasmas such as intensity, emission lifetime and line broadening.
From the Cambridge English Corpus
applied pressureHe also considered the effects of an applied pressure gradient.
From the Cambridge English Corpus
These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors.
See all collocations with pressure
What is the pronunciation of pressure?
C2,C1,B2,B2
Translations of pressure
in Chinese (Traditional)
推, 壓力, （液體或氣體產生的）壓力…
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in Chinese (Simplified)
推, 压力, （液体或气体产生的）压力，压强…
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in Spanish
presión, problema, presionar…
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in Portuguese
pressão, pressionar, pressão [feminine]…
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in more languages
in Marathi
in Japanese
in Turkish
in French
in Catalan
in Dutch
in Tamil
in Hindi
in Gujarati
in Danish
in Swedish
in Malay
in German
in Norwegian
in Urdu
in Ukrainian
in Russian
in Telugu
in Arabic
in Bengali
in Czech
in Indonesian
in Thai
in Vietnamese
in Polish
in Korean
in Italian
जोर लावणे, जोरात दाबणे, दाब…
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（人に対する）圧力, 強制力, （精神的な）プレッシャー…
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baskı, tazyik, zorlama…
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pression [feminine], faire pression sur, pression…
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pressió, problema, pressionar…
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druk…
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நீங்கள் எதையாவது அழுத்தும்போது நீங்கள் உருவாக்கும் விசை, ஒரு திரவம் அல்லது வாயு ஒரு பகுதிக்கு எதிராக அழுத்தும்போது அது உருவாக்கும் விசை, வாக்குவாதம்…
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(दबाने या धकेलने के कारण उत्पन्न) दबाव, (तरल या गैस का) दाब, दबाव…
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દબાવવું, દબાણ, મુશ્કેલ પરિસ્થિતિ જે તમને બેચેન અથવા નાખુશ બનાવે છે…
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tryk, pres, tvang…
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tryck, press, stress…
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tekanan, desakan…
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der Druck…
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press [neuter], påvirkning [masculine], stress [masculine]…
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دباؤ, گیس یا کسی سیال چیز کا دباؤ, تناؤ…
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стискання, тиск, гніт…
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давление, воздействие, напряжение…
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మీరు దేనినైనా నొక్కినప్పుడు మీరు ఉత్పత్తి చేసే శక్తి, ద్రవాన్ని లేదా వాయువును ఒక ప్రదేశం మీద నొక్కినప్పుడు ఉత్పత్తి అయే శక్తి, ఒత్తిడి…
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ضَغْط, يَمارِس ضَغطا عَلى…
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চাপ দেওয়া, তরল বা গ্যাসের দ্বারা সৃষ্ট চাপ, চাপ…
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tlak, tíha, (ná)tlak…
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tekanan, paksaan…
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การกด, ความกดดัน, แรงกระตุ้น…
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lực, áp suất, áp lực…
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presja, naciski, stres…
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압박, 압박감, 스트레스…
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pressione, fare pressione su…
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pressed
presser
pressing
pressingly
pressure
pressure altitude
BETA
pressure cooker
pressure gauge
BETA
pressure group
More meanings of pressure
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blood pressure
high blood pressure
peer pressure
pressure cooker
air pressure
high-pressure
low-pressure
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response
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/rɪˈspɒns/
US
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/rɪˈspɑːns/
an answer or reaction
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Contents
English
Noun
pressure (PUSHING)
pressure (PERSUADING)
so no pressure then!
Verb
American
Noun
pressure (FORCE)
pressure (INFLUENCE)
pressure (WORRY)
Verb
pressure
Business
Noun
pressure
put pressure on sb/sth
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Pressure - Wikipedia
Pressure - Wikipedia
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1Definition
Toggle Definition subsection
1.1Formula
1.2Units
1.3Examples
1.4Scalar nature
2Types
Toggle Types subsection
2.1Fluid pressure
2.1.1Applications
2.2Explosion or deflagration pressures
2.3Negative pressures
2.4Stagnation pressure
2.5Surface pressure and surface tension
2.6Pressure of an ideal gas
2.7Vapour pressure
2.8Liquid pressure
2.9Direction of liquid pressure
2.10Kinematic pressure
2.10.1Navier–Stokes equation with kinematic quantities
3See also
4Notes
5References
6External links
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Pressure
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From Wikipedia, the free encyclopedia
Force distributed over an area
This article is about pressure in the physical sciences. For other uses, see Pressure (disambiguation).
PressurePressure exerted by particle collisions inside a closed container. The collisions that exert the pressure are highlighted in red.Common symbolsp, PSI unitpascal (Pa)In SI base unitskg⋅m−1⋅s−2Derivations fromother quantitiesp = F / ADimension
M
L
−
1
T
−
2
{\displaystyle {\mathsf {M}}{\mathsf {L}}^{-1}{\mathsf {T}}^{-2}}
ThermodynamicsThe classical Carnot heat engine
Branches
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System propertiesNote: Conjugate variables in italics
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Specific heat capacity
c
=
{\displaystyle c=}
T
{\displaystyle T}
∂
S
{\displaystyle \partial S}
N
{\displaystyle N}
∂
T
{\displaystyle \partial T}
Compressibility
β
=
−
{\displaystyle \beta =-}
1
{\displaystyle 1}
∂
V
{\displaystyle \partial V}
V
{\displaystyle V}
∂
p
{\displaystyle \partial p}
Thermal expansion
α
=
{\displaystyle \alpha =}
1
{\displaystyle 1}
∂
V
{\displaystyle \partial V}
V
{\displaystyle V}
∂
T
{\displaystyle \partial T}
Equations
Carnot's theorem
Clausius theorem
Fundamental relation
Ideal gas law
Maxwell relations
Onsager reciprocal relations
Bridgman's equations
Table of thermodynamic equations
Potentials
Free energy
Free entropy
Internal energy
U
(
S
,
V
)
{\displaystyle U(S,V)}
Enthalpy
H
(
S
,
p
)
=
U
+
p
V
{\displaystyle H(S,p)=U+pV}
Helmholtz free energy
A
(
T
,
V
)
=
U
−
T
S
{\displaystyle A(T,V)=U-TS}
Gibbs free energy
G
(
T
,
p
)
=
H
−
T
S
{\displaystyle G(T,p)=H-TS}
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Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.[1]: 445 Gauge pressure (also spelled gage pressure)[a] is the pressure relative to the ambient pressure.
Various units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the SI unit of pressure, the pascal (Pa), for example, is one newton per square metre (N/m2); similarly, the pound-force per square inch (psi, symbol lbf/in2) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, and inch of mercury are used to express pressures in terms of the height of column of a particular fluid in a manometer.
Definition[edit]
Pressure is the amount of force applied perpendicular to the surface of an object per unit area. The symbol for it is "p" or P.[2]
The IUPAC recommendation for pressure is a lower-case p.[3]
However, upper-case P is widely used. The usage of P vs p depends upon the field in which one is working, on the nearby presence of other symbols for quantities such as power and momentum, and on writing style.
Formula[edit]
Conjugate variablesof thermodynamics
Pressure Volume (Stress) (Strain) Temperature Entropy Chemical potential Particle number
Mathematically:[4]
p
=
F
A
,
{\displaystyle p={\frac {F}{A}},}
where:
p
{\displaystyle p}
is the pressure,
F
{\displaystyle F}
is the magnitude of the normal force,
A
{\displaystyle A}
is the area of the surface on contact.
Pressure is a scalar quantity. It relates the vector area element (a vector normal to the surface) with the normal force acting on it. The pressure is the scalar proportionality constant that relates the two normal vectors:
d
F
n
=
−
p
d
A
=
−
p
n
d
A
.
{\displaystyle d\mathbf {F} _{n}=-p\,d\mathbf {A} =-p\,\mathbf {n} \,dA.}
The minus sign comes from the convention that the force is considered towards the surface element, while the normal vector points outward. The equation has meaning in that, for any surface S in contact with the fluid, the total force exerted by the fluid on that surface is the surface integral over S of the right-hand side of the above equation.
It is incorrect (although rather usual) to say "the pressure is directed in such or such direction". The pressure, as a scalar, has no direction. The force given by the previous relationship to the quantity has a direction, but the pressure does not. If we change the orientation of the surface element, the direction of the normal force changes accordingly, but the pressure remains the same.[citation needed]
Pressure is distributed to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. It is a fundamental parameter in thermodynamics, and it is conjugate to volume.[5]
Units[edit]
Mercury column
The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N/m2, or kg·m−1·s−2). This name for the unit was added in 1971;[6] before that, pressure in SI was expressed in newtons per square metre.
Other units of pressure, such as pounds per square inch (lbf/in2) and bar, are also in common use. The CGS unit of pressure is the barye (Ba), equal to 1 dyn·cm−2, or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre ("g/cm2" or "kg/cm2") and the like without properly identifying the force units. But using the names kilogram, gram, kilogram-force, or gram-force (or their symbols) as units of force is deprecated in SI. The technical atmosphere (symbol: at) is 1 kgf/cm2 (98.0665 kPa, or 14.223 psi).
Pressure is related to energy density and may be expressed in units such as joules per cubic metre (J/m3, which is equal to Pa).
Mathematically:
p
=
F
⋅
distance
A
⋅
distance
=
Work
Volume
=
Energy (J)
Volume
(
m
3
)
.
{\displaystyle p={\frac {F\cdot {\text{distance}}}{A\cdot {\text{distance}}}}={\frac {\text{Work}}{\text{Volume}}}={\frac {\text{Energy (J)}}{{\text{Volume }}({\text{m}}^{3})}}.}
Some meteorologists prefer the hectopascal (hPa) for atmospheric air pressure, which is equivalent to the older unit millibar (mbar). Similar pressures are given in kilopascals (kPa) in most other fields, except aviation where the hecto- prefix is commonly used. The inch of mercury is still used in the United States. Oceanographers usually measure underwater pressure in decibars (dbar) because pressure in the ocean increases by approximately one decibar per metre depth.
The standard atmosphere (atm) is an established constant. It is approximately equal to typical air pressure at Earth mean sea level and is defined as 101325 Pa.
Because pressure is commonly measured by its ability to displace a column of liquid in a manometer, pressures are often expressed as a depth of a particular fluid (e.g., centimetres of water, millimetres of mercury or inches of mercury). The most common choices are mercury (Hg) and water; water is nontoxic and readily available, while mercury's high density allows a shorter column (and so a smaller manometer) to be used to measure a given pressure. The pressure exerted by a column of liquid of height h and density ρ is given by the hydrostatic pressure equation p = ρgh, where g is the gravitational acceleration. Fluid density and local gravity can vary from one reading to another depending on local factors, so the height of a fluid column does not define pressure precisely.
When millimetres of mercury (or inches of mercury) are quoted today, these units are not based on a physical column of mercury; rather, they have been given precise definitions that can be expressed in terms of SI units.[7] One millimetre of mercury is approximately equal to one torr. The water-based units still depend on the density of water, a measured, rather than defined, quantity. These manometric units are still encountered in many fields. Blood pressure is measured in millimetres (or centimetres) of mercury in most of the world, and lung pressures in centimetres of water are still common.[citation needed]
Underwater divers use the metre sea water (msw or MSW) and foot sea water (fsw or FSW) units of pressure, and these are the units for pressure gauges used to measure pressure exposure in diving chambers and personal decompression computers. A msw is defined as 0.1 bar (= 10,000 Pa), is not the same as a linear metre of depth. 33.066 fsw = 1 atm[citation needed] (1 atm = 101,325 Pa / 33.066 = 3,064.326 Pa). The pressure conversion from msw to fsw is different from the length conversion: 10 msw = 32.6336 fsw, while 10 m = 32.8083 ft.[citation needed]
Gauge pressure is often given in units with "g" appended, e.g. "kPag", "barg" or "psig", and units for measurements of absolute pressure are sometimes given a suffix of "a", to avoid confusion, for example "kPaa", "psia". However, the US National Institute of Standards and Technology recommends that, to avoid confusion, any modifiers be instead applied to the quantity being measured rather than the unit of measure.[8] For example, "pg = 100 psi" rather than "p = 100 psig".
Differential pressure is expressed in units with "d" appended; this type of measurement is useful when considering sealing performance or whether a valve will open or close.
Presently or formerly popular pressure units include the following:
atmosphere (atm)
manometric units:
centimetre, inch, millimetre (torr) and micrometre (mTorr, micron) of mercury,
height of equivalent column of water, including millimetre (mm H2O), centimetre (cm H2O), metre, inch, and foot of water;
imperial and customary units:
kip, short ton-force, long ton-force, pound-force, ounce-force, and poundal per square inch,
short ton-force and long ton-force per square inch,
fsw (feet sea water) used in underwater diving, particularly in connection with diving pressure exposure and decompression;
non-SI metric units:
bar, decibar, millibar,
msw (metres sea water), used in underwater diving, particularly in connection with diving pressure exposure and decompression,
kilogram-force, or kilopond, per square centimetre (technical atmosphere),
gram-force and tonne-force (metric ton-force) per square centimetre,
barye (dyne per square centimetre),
kilogram-force and tonne-force per square metre,
sthene per square metre (pieze).
Examples[edit]
The effects of an external pressure of 700 bar on an aluminum cylinder with 5 mm (0.197 in) wall thickness
As an example of varying pressures, a finger can be pressed against a wall without making any lasting impression; however, the same finger pushing a thumbtack can easily damage the wall. Although the force applied to the surface is the same, the thumbtack applies more pressure because the point concentrates that force into a smaller area. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point. Unlike stress, pressure is defined as a scalar quantity. The negative gradient of pressure is called the force density.[9]
Another example is a knife. If the flat edge is used, force is distributed over a larger surface area resulting in less pressure, and it will not cut. Whereas using the sharp edge, which has less surface area, results in greater pressure, and so the knife cuts smoothly. This is one example of a practical application of pressure[10]
For gases, pressure is sometimes measured not as an absolute pressure, but relative to atmospheric pressure; such measurements are called gauge pressure. An example of this is the air pressure in an automobile tire, which might be said to be "220 kPa (32 psi)", but is actually 220 kPa (32 psi) above atmospheric pressure. Since atmospheric pressure at sea level is about 100 kPa (14.7 psi), the absolute pressure in the tire is therefore about 320 kPa (46 psi). In technical work, this is written "a gauge pressure of 220 kPa (32 psi)".
Where space is limited, such as on pressure gauges, name plates, graph labels, and table headings, the use of a modifier in parentheses, such as "kPa (gauge)" or "kPa (absolute)", is permitted. In non-SI technical work, a gauge pressure of 32 psi (220 kPa) is sometimes written as "32 psig", and an absolute pressure as "32 psia", though the other methods explained above that avoid attaching characters to the unit of pressure are preferred.[8]
Gauge pressure is the relevant measure of pressure wherever one is interested in the stress on storage vessels and the plumbing components of fluidics systems. However, whenever equation-of-state properties, such as densities or changes in densities, must be calculated, pressures must be expressed in terms of their absolute values. For instance, if the atmospheric pressure is 100 kPa (15 psi), a gas (such as helium) at 200 kPa (29 psi) (gauge) (300 kPa or 44 psi [absolute]) is 50% denser than the same gas at 100 kPa (15 psi) (gauge) (200 kPa or 29 psi [absolute]). Focusing on gauge values, one might erroneously conclude the first sample had twice the density of the second one.[citation needed]
Scalar nature[edit]
In a static gas, the gas as a whole does not appear to move. The individual molecules of the gas, however, are in constant random motion. Because there are an extremely large number of molecules and because the motion of the individual molecules is random in every direction, no motion is detected. When the gas is at least partially confined (that is, not free to expand rapidly), the gas will exhibit a hydrostatic pressure. This confinement can be achieved with either a physical container of some sort, or in a gravitational well such as a planet, otherwise known as atmospheric pressure.
In the case of planetary atmospheres, the pressure-gradient force of the gas pushing outwards from higher pressure, lower altitudes to lower pressure, higher altitudes is balanced by the gravitational force, preventing the gas from diffusing into outer space and maintaining hydrostatic equilibrium.
In a physical container, the pressure of the gas originates from the molecules colliding with the walls of the container. The walls of the container can be anywhere inside the gas, and the force per unit area (the pressure) is the same. If the "container" is shrunk down to a very small point (becoming less true as the atomic scale is approached), the pressure will still have a single value at that point. Therefore, pressure is a scalar quantity, not a vector quantity. It has magnitude but no direction sense associated with it. Pressure force acts in all directions at a point inside a gas. At the surface of a gas, the pressure force acts perpendicular (at right angle) to the surface.[11]
A closely related quantity is the stress tensor σ, which relates the vector force
F
{\displaystyle \mathbf {F} }
to the
vector area
A
{\displaystyle \mathbf {A} }
via the linear relation
F
=
σ
A
{\displaystyle \mathbf {F} =\sigma \mathbf {A} }
.
This tensor may be expressed as the sum of the viscous stress tensor minus the hydrostatic pressure. The negative of the stress tensor is sometimes called the pressure tensor, but in the following, the term "pressure" will refer only to the scalar pressure.[12]
According to the theory of general relativity, pressure increases the strength of a gravitational field (see stress–energy tensor) and so adds to the mass-energy cause of gravity. This effect is unnoticeable at everyday pressures but is significant in neutron stars, although it has not been experimentally tested.[13]
Types[edit]
Fluid pressure[edit]
Fluid pressure is most often the compressive stress at some point within a fluid. (The term fluid refers to both liquids and gases – for more information specifically about liquid pressure, see section below.)
Water escapes at high speed from a damaged hydrant that contains water at high pressure
Fluid pressure occurs in one of two situations:
An open condition, called "open channel flow", e.g. the ocean, a swimming pool, or the atmosphere.
A closed condition, called "closed conduit", e.g. a water line or gas line.
Pressure in open conditions usually can be approximated as the pressure in "static" or non-moving conditions (even in the ocean where there are waves and currents), because the motions create only negligible changes in the pressure. Such conditions conform with principles of fluid statics. The pressure at any given point of a non-moving (static) fluid is called the hydrostatic pressure.
Closed bodies of fluid are either "static", when the fluid is not moving, or "dynamic", when the fluid can move as in either a pipe or by compressing an air gap in a closed container. The pressure in closed conditions conforms with the principles of fluid dynamics.
The concepts of fluid pressure are predominantly attributed to the discoveries of Blaise Pascal and Daniel Bernoulli. Bernoulli's equation can be used in almost any situation to determine the pressure at any point in a fluid. The equation makes some assumptions about the fluid, such as the fluid being ideal[14] and incompressible.[14] An ideal fluid is a fluid in which there is no friction, it is inviscid[14] (zero viscosity).[14] The equation for all points of a system filled with a constant-density fluid is[15]
p
γ
+
v
2
2
g
+
z
=
c
o
n
s
t
,
{\displaystyle {\frac {p}{\gamma }}+{\frac {v^{2}}{2g}}+z=\mathrm {const} ,}
where:
p, pressure of the fluid,
γ
{\displaystyle {\gamma }}
= ρg, density × acceleration of gravity is the (volume-) specific weight of the fluid,[14]
v, velocity of the fluid,
g, acceleration of gravity,
z, elevation,
p
γ
{\displaystyle {\frac {p}{\gamma }}}
, pressure head,
v
2
2
g
{\displaystyle {\frac {v^{2}}{2g}}}
, velocity head.
Applications[edit]
Hydraulic brakes
Artesian well
Blood pressure
Hydraulic head
Plant cell turgidity
Pythagorean cup
Pressure washing
Explosion or deflagration pressures[edit]
Explosion or deflagration pressures are the result of the ignition of explosive gases, mists, dust/air suspensions, in unconfined and confined spaces.
Negative pressures[edit]
Low-pressure chamber in Bundesleistungszentrum Kienbaum, Germany
While pressures are, in general, positive, there are several situations in which negative pressures may be encountered:
When dealing in relative (gauge) pressures. For instance, an absolute pressure of 80 kPa may be described as a gauge pressure of −21 kPa (i.e., 21 kPa below an atmospheric pressure of 101 kPa). For example, abdominal decompression is an obstetric procedure during which negative gauge pressure is applied intermittently to a pregnant woman's abdomen.
Negative absolute pressures are possible. They are effectively tension, and both bulk solids and bulk liquids can be put under negative absolute pressure by pulling on them.[16] Microscopically, the molecules in solids and liquids have attractive interactions that overpower the thermal kinetic energy, so some tension can be sustained. Thermodynamically, however, a bulk material under negative pressure is in a metastable state, and it is especially fragile in the case of liquids where the negative pressure state is similar to superheating and is easily susceptible to cavitation.[17] In certain situations, the cavitation can be avoided and negative pressures sustained indefinitely,[17] for example, liquid mercury has been observed to sustain up to −425 atm in clean glass containers.[18] Negative liquid pressures are thought to be involved in the ascent of sap in plants taller than 10 m (the atmospheric pressure head of water).[19]
The Casimir effect can create a small attractive force due to interactions with vacuum energy; this force is sometimes termed "vacuum pressure" (not to be confused with the negative gauge pressure of a vacuum).
For non-isotropic stresses in rigid bodies, depending on how the orientation of a surface is chosen, the same distribution of forces may have a component of positive stress along one surface normal, with a component of negative stress acting along another surface normal. The pressure is then defined as the average of the three principal stresses.
The stresses in an electromagnetic field are generally non-isotropic, with the stress normal to one surface element (the normal stress) being negative, and positive for surface elements perpendicular to this.
In cosmology, dark energy creates a very small yet cosmically significant amount of negative pressure, which accelerates the expansion of the universe.
Stagnation pressure[edit]
Main article: Stagnation pressure
Stagnation pressure is the pressure a fluid exerts when it is forced to stop moving. Consequently, although a fluid moving at higher speed will have a lower static pressure, it may have a higher stagnation pressure when forced to a standstill. Static pressure and stagnation pressure are related by:
p
0
=
1
2
ρ
v
2
+
p
{\displaystyle p_{0}={\frac {1}{2}}\rho v^{2}+p}
where
p
0
{\displaystyle p_{0}}
is the stagnation pressure,
ρ
{\displaystyle \rho }
is the density,
v
{\displaystyle v}
is the flow velocity,
p
{\displaystyle p}
is the static pressure.
The pressure of a moving fluid can be measured using a Pitot tube, or one of its variations such as a Kiel probe or Cobra probe, connected to a manometer. Depending on where the inlet holes are located on the probe, it can measure static pressures or stagnation pressures.
Surface pressure and surface tension[edit]
There is a two-dimensional analog of pressure – the lateral force per unit length applied on a line perpendicular to the force.
Surface pressure is denoted by π:
π
=
F
l
{\displaystyle \pi ={\frac {F}{l}}}
and shares many similar properties with three-dimensional pressure. Properties of surface chemicals can be investigated by measuring pressure/area isotherms, as the two-dimensional analog of Boyle's law, πA = k, at constant temperature.
Surface tension is another example of surface pressure, but with a reversed sign, because "tension" is the opposite to "pressure".
Pressure of an ideal gas[edit]
Main article: Ideal gas law
In an ideal gas, molecules have no volume and do not interact. According to the ideal gas law, pressure varies linearly with temperature and quantity, and inversely with volume:
p
=
n
R
T
V
,
{\displaystyle p={\frac {nRT}{V}},}
where:
p is the absolute pressure of the gas,
n is the amount of substance,
T is the absolute temperature,
V is the volume,
R is the ideal gas constant.
Real gases exhibit a more complex dependence on the variables of state.[20]
Vapour pressure[edit]
Main article: Vapour pressure
Vapour pressure is the pressure of a vapour in thermodynamic equilibrium with its condensed phases in a closed system. All liquids and solids have a tendency to evaporate into a gaseous form, and all gases have a tendency to condense back to their liquid or solid form.
The atmospheric pressure boiling point of a liquid (also known as the normal boiling point) is the temperature at which the vapor pressure equals the ambient atmospheric pressure. With any incremental increase in that temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and lift the liquid to form vapour bubbles inside the bulk of the substance. Bubble formation deeper in the liquid requires a higher pressure, and therefore higher temperature, because the fluid pressure increases above the atmospheric pressure as the depth increases.
The vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial vapor pressure.
Liquid pressure[edit]
See also: Fluid statics § Pressure in fluids at rest
Part of a series onContinuum mechanics
J
=
−
D
d
φ
d
x
{\displaystyle J=-D{\frac {d\varphi }{dx}}}
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Energy
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vte
When a person swims under the water, water pressure is felt acting on the person's eardrums. The deeper that person swims, the greater the pressure. The pressure felt is due to the weight of the water above the person. As someone swims deeper, there is more water above the person and therefore greater pressure. The pressure a liquid exerts depends on its depth.
Liquid pressure also depends on the density of the liquid. If someone was submerged in a liquid more dense than water, the pressure would be correspondingly greater. Thus, we can say that the depth, density and liquid pressure are directly proportionate. The pressure due to a liquid in liquid columns of constant density or at a depth within a substance is represented by the following formula:
p
=
ρ
g
h
,
{\displaystyle p=\rho gh,}
where:
p is liquid pressure,
g is gravity at the surface of overlaying material,
ρ is density of liquid,
h is height of liquid column or depth within a substance.
Another way of saying the same formula is the following:
p
=
weight density
×
depth
.
{\displaystyle p={\text{weight density}}\times {\text{depth}}.}
Derivation of this equation
This is derived from the definitions of pressure and weight density. Consider an area at the bottom of a vessel of liquid. The weight of the column of liquid directly above this area produces pressure. From the definition
weight density
=
weight
volume
{\displaystyle {\text{weight density}}={\frac {\text{weight}}{\text{volume}}}}
we can express this weight of liquid as
weight
=
weight density
×
volume
,
{\displaystyle {\text{weight}}={\text{weight density}}\times {\text{volume}},}
where the volume of the column is simply the area multiplied by the depth. Then we have
pressure
=
force
area
=
weight
area
=
weight density
×
volume
area
,
{\displaystyle {\text{pressure}}={\frac {\text{force}}{\text{area}}}={\frac {\text{weight}}{\text{area}}}={\frac {{\text{weight density}}\times {\text{volume}}}{\text{area}}},}
pressure
=
weight density
×
(area
×
depth)
area
.
{\displaystyle {\text{pressure}}={\frac {{\text{weight density}}\times {\text{(area}}\times {\text{depth)}}}{\text{area}}}.}
With the "area" in the numerator and the "area" in the denominator canceling each other out, we are left with
pressure
=
weight density
×
depth
.
{\displaystyle {\text{pressure}}={\text{weight density}}\times {\text{depth}}.}
Written with symbols, this is our original equation:
p
=
ρ
g
h
.
{\displaystyle p=\rho gh.}
The pressure a liquid exerts against the sides and bottom of a container depends on the density and the depth of the liquid. If atmospheric pressure is neglected, liquid pressure against the bottom is twice as great at twice the depth; at three times the depth, the liquid pressure is threefold; etc. Or, if the liquid is two or three times as dense, the liquid pressure is correspondingly two or three times as great for any given depth. Liquids are practically incompressible – that is, their volume can hardly be changed by pressure (water volume decreases by only 50 millionths of its original volume for each atmospheric increase in pressure). Thus, except for small changes produced by temperature, the density of a particular liquid is practically the same at all depths.
Atmospheric pressure pressing on the surface of a liquid must be taken into account when trying to discover the total pressure acting on a liquid. The total pressure of a liquid, then, is ρgh plus the pressure of the atmosphere. When this distinction is important, the term total pressure is used. Otherwise, discussions of liquid pressure refer to pressure without regard to the normally ever-present atmospheric pressure.
The pressure does not depend on the amount of liquid present. Volume is not the important factor – depth is. The average water pressure acting against a dam depends on the average depth of the water and not on the volume of water held back. For example, a wide but shallow lake with a depth of 3 m (10 ft) exerts only half the average pressure that a small 6 m (20 ft) deep pond does. (The total force applied to the longer dam will be greater, due to the greater total surface area for the pressure to act upon. But for a given 5-foot (1.5 m)-wide section of each dam, the 10 ft (3.0 m) deep water will apply one quarter the force of 20 ft (6.1 m) deep water). A person will feel the same pressure whether their head is dunked a metre beneath the surface of the water in a small pool or to the same depth in the middle of a large lake.
If four interconnected vases contain different amounts of water but are all filled to equal depths, then a fish with its head dunked a few centimetres under the surface will be acted on by water pressure that is the same in any of the vases. If the fish swims a few centimetres deeper, the pressure on the fish will increase with depth and be the same no matter which vase the fish is in. If the fish swims to the bottom, the pressure will be greater, but it makes no difference which vase it is in. All vases are filled to equal depths, so the water pressure is the same at the bottom of each vase, regardless of its shape or volume. If water pressure at the bottom of a vase were greater than water pressure at the bottom of a neighboring vase, the greater pressure would force water sideways and then up the narrower vase to a higher level until the pressures at the bottom were equalized. Pressure is depth dependent, not volume dependent, so there is a reason that water seeks its own level.
Restating this as an energy equation, the energy per unit volume in an ideal, incompressible liquid is constant throughout its vessel. At the surface, gravitational potential energy is large but liquid pressure energy is low. At the bottom of the vessel, all the gravitational potential energy is converted to pressure energy. The sum of pressure energy and gravitational potential energy per unit volume is constant throughout the volume of the fluid and the two energy components change linearly with the depth.[21] Mathematically, it is described by Bernoulli's equation, where velocity head is zero and comparisons per unit volume in the vessel are
p
γ
+
z
=
c
o
n
s
t
.
{\displaystyle {\frac {p}{\gamma }}+z=\mathrm {const} .}
Terms have the same meaning as in section Fluid pressure.
Direction of liquid pressure[edit]
An experimentally determined fact about liquid pressure is that it is exerted equally in all directions.[22] If someone is submerged in water, no matter which way that person tilts their head, the person will feel the same amount of water pressure on their ears. Because a liquid can flow, this pressure is not only downward. Pressure is seen acting sideways when water spurts sideways from a leak in the side of an upright can. Pressure also acts upward, as demonstrated when someone tries to push a beach ball beneath the surface of the water. The bottom of a boat is pushed upward by water pressure (buoyancy).
When a liquid presses against a surface, there is a net force that is perpendicular to the surface. Although pressure does not have a specific direction, force does. A submerged triangular block has water forced against each point from many directions, but components of the force that are not perpendicular to the surface cancel each other out, leaving only a net perpendicular point.[22] This is why water spurting from a hole in a bucket initially exits the bucket in a direction at right angles to the surface of the bucket in which the hole is located. Then it curves downward due to gravity. If there are three holes in a bucket (top, bottom, and middle), then the force vectors perpendicular to the inner container surface will increase with increasing depth – that is, a greater pressure at the bottom makes it so that the bottom hole will shoot water out the farthest. The force exerted by a fluid on a smooth surface is always at right angles to the surface. The speed of liquid out of the hole is
2
g
h
{\displaystyle \scriptstyle {\sqrt {2gh}}}
, where h is the depth below the free surface.[22] This is the same speed the water (or anything else) would have if freely falling the same vertical distance h.
Kinematic pressure[edit]
P
=
p
/
ρ
0
{\displaystyle P=p/\rho _{0}}
is the kinematic pressure, where
p
{\displaystyle p}
is the pressure and
ρ
0
{\displaystyle \rho _{0}}
constant mass density. The SI unit of P is m2/s2. Kinematic pressure is used in the same manner as kinematic viscosity
ν
{\displaystyle \nu }
in order to compute the Navier–Stokes equation without explicitly showing the density
ρ
0
{\displaystyle \rho _{0}}
.
Navier–Stokes equation with kinematic quantities[edit]
∂
u
∂
t
+
(
u
∇
)
u
=
−
∇
P
+
ν
∇
2
u
.
{\displaystyle {\frac {\partial u}{\partial t}}+(u\nabla )u=-\nabla P+\nu \nabla ^{2}u.}
See also[edit]
Boyle's law – Relation between gas pressure and volume
Combined gas law – Combination of Charles', Boyle's and Gay-Lussac's gas laws
Conversion of units – Comparison of various scales
Critical point (thermodynamics) – Temperature and pressure point where phase boundaries disappear
Dimensional analysis – Analysis of the relationships between different physical quantities
Dynamic pressure – Kinetic energy per unit volume of a fluid
Electric potential – Line integral of the electric field
Electron degeneracy pressure – Repulsive force in quantum mechanics
High pressure – Great force distributed over a small area
Hydraulics – Applied engineering involving liquids
Hydrostatic stress – Component of mechanical stress without shear
Internal pressure – measure of how the internal energy of a system changes when it expands or contracts at constant temperaturePages displaying wikidata descriptions as a fallback
Kinetic theory – Understanding of gas properties in terms of molecular motion
Microphone – Device that converts sound into an electrical signal
Orders of magnitude (pressure)
Partial pressure – Pressure of a component gas in a mixture
Pressure measurement – Analysis of force applied by a fluid on a surface
Pressure sensor – Analysis of force applied by a fluid on a surfacePages displaying short descriptions of redirect targets
Sound pressure – Local pressure deviation caused by a sound wave
Static pressure – Term in fluid mechanics
Timeline of temperature and pressure measurement technology
Torricelli's law – Theorem in fluid mechanics
Vacuum pump – Equipment generating a relative vacuum
Vertical pressure variation – Variation in pressure as a function of elevation
Notes[edit]
^ The preferred spelling varies by country and even by industry. Further, both spellings are often used within a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling.
References[edit]
^ Knight, PhD, Randall D. (2007). "Fluid Mechanics". Physics for Scientists and Engineers: A Strategic Approach (google books) (2nd ed.). San Francisco: Pearson Addison Wesley. p. 1183. ISBN 978-0-321-51671-8. Retrieved 6 April 2020. Pressure itself is not a Force, even though we sometimes talk "informally" about the "force exerted by the pressure. The correct statement is that the Fluid exerts a force on a surface. In addition, Pressure is a scalar, not a vector.
^
Giancoli, Douglas G. (2004). Physics: principles with applications. Upper Saddle River, N.J.: Pearson Education. ISBN 978-0-13-060620-4.
^
McNaught, A. D.; Wilkinson, A.; Nic, M.; Jirat, J.; Kosata, B.; Jenkins, A. (2014). IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). 2.3.3. Oxford: Blackwell Scientific Publications. doi:10.1351/goldbook.P04819. ISBN 978-0-9678550-9-7. Archived from the original on 2016-03-04.
^ R Nave. "Pressure". Hyperphysics. Georgia State University, Dept. of Physics and Astronomy. Retrieved 2022-03-05.
^ Alberty, Robert A. (2001). "USE OF LEGENDRE TRANSFORMS IN CHEMICAL THERMODYNAMICS (IUPAC Technical Report)" (PDF). Pure Appl. Chem. 73 (8): 1349–1380. doi:10.1351/pac200173081349. S2CID 98264934. Retrieved 1 November 2021. See Table 1 Conjugate pairs of variables ... (p.1357)
^ "14th Conference of the International Bureau of Weights and Measures". Bipm.fr. Archived from the original on 2007-06-30. Retrieved 2012-03-27.
^ International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), p. 127, ISBN 92-822-2213-6, archived (PDF) from the original on 2021-06-04, retrieved 2021-12-16
^ a b "Rules and Style Conventions for Expressing Values of Quantities". NIST. 2 July 2009. Archived from the original on 2009-07-10. Retrieved 2009-07-07.
^ Lautrup, Benny (2005). Physics of continuous matter : exotic and everyday phenomena in the macroscopic world. Bristol: Institute of Physics. p. 50. ISBN 9780750307529.
^ Breithaupt, Jim (2015). Physics (Fourth ed.). Basingstoke: Palgrave Macmillan. p. 106. ISBN 9781137443243.
^ "Gas Pressure Study Guide - Inspirit Learning Inc". 2023-03-28. Retrieved 2024-02-11.
^ "Thermal-FluidsPedia | Pressure (Thermodynamics) | Thermal-Fluids Central". www.thermalfluidscentral.org. Retrieved 2024-02-11.
^ Vishwakarma, Ram Gopal (2009). "Einstein's gravity under pressure". Astrophysics and Space Science. 321 (2): 151–156. arXiv:0705.0825. Bibcode:2009Ap&SS.321..151V. doi:10.1007/s10509-009-0016-8. S2CID 218673952.
^ a b c d e Finnemore, John, E. and Joseph B. Franzini (2002). Fluid Mechanics: With Engineering Applications. New York: McGraw Hill, Inc. pp. 14–29. ISBN 978-0-07-243202-2.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ NCEES (2011). Fundamentals of Engineering: Supplied Reference Handbook. Clemson, South Carolina: NCEES. p. 64. ISBN 978-1-932613-59-9.
^ Imre, A. R. (2007). "How to generate and measure negative pressure in liquids?". Soft Matter under Exogenic Impacts. NATO Science Series II: Mathematics, Physics and Chemistry. Vol. 242. pp. 379–388. doi:10.1007/978-1-4020-5872-1_24. ISBN 978-1-4020-5871-4. ISSN 1568-2609.
^ a b Imre, A. R; Maris, H. J; Williams, P. R, eds. (2002). Liquids Under Negative Pressure (Nato Science Series II). Springer. doi:10.1007/978-94-010-0498-5. ISBN 978-1-4020-0895-5.
^ Briggs, Lyman J. (1953). "The Limiting Negative Pressure of Mercury in Pyrex Glass". Journal of Applied Physics. 24 (4): 488–490. Bibcode:1953JAP....24..488B. doi:10.1063/1.1721307. ISSN 0021-8979.
^ Karen Wright (March 2003). "The Physics of Negative Pressure". Discover. Archived from the original on 8 January 2015. Retrieved 31 January 2015.
^ P. Atkins, J. de Paula Elements of Physical Chemistry, 4th Ed, W. H. Freeman, 2006. ISBN 0-7167-7329-5.
^ Streeter, V. L., Fluid Mechanics, Example 3.5, McGraw–Hill Inc. (1966), New York.
^ a b c Hewitt 251 (2006)[full citation needed]
External links[edit]
Introduction to Fluid Statics and Dynamics on Project PHYSNET
Pressure being a scalar quantity
wikiUnits.org - Convert units of pressure
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Pressure | Definition, Measurement, & Types | Britannica
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Also known as: bulk stress
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pressure, in the physical sciences, the perpendicular force per unit area, or the stress at a point within a confined fluid. The pressure exerted on a floor by a 42-pound box the bottom of which has an area of 84 square inches is equal to the force divided by the area over which it is exerted; i.e., it is one-half pound per square inch. The weight of the atmosphere pushing down on each unit area of Earth’s surface constitutes atmospheric pressure, which at sea level is about 15 pounds per square inch. In SI units, pressure is measured in pascals; one pascal equals one newton per square metre. Atmospheric pressure is close to 100,000 pascals.ideal gas lawAccording to the ideal gas law, when a gas is compressed into a smaller volume, the number and velocity of molecular collisions increase, raising the gas's temperature and pressure.(more)The pressure exerted by a confined gas results from the average effect of the forces produced on the container walls by the rapid and continual bombardment of the huge number of gas molecules. Absolute pressure of a gas or liquid is the total pressure it exerts, including the effect of atmospheric pressure. An absolute pressure of zero corresponds to empty space or a complete vacuum.
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Physics and Natural Law
Measurement of pressures by ordinary gauges on Earth, such as a tire-pressure gauge, expresses pressure in excess of atmospheric. Thus, a tire gauge may indicate a pressure of 30 pounds (per square inch), the gauge pressure. The absolute pressure exerted by the air within the tire, including atmospheric pressure, is 45 pounds per square inch. Pressures less than atmospheric are negative gauge pressures that correspond to partial vacuums.diffusion of water across a semipermeable membrane(A) Water diffuses down its concentration gradient from side 1 to side 2 of a rigid container to dilute the impermeant substance. (B) The net flux of the water increases the hydrostatic pressure on side 2, tending to force the water back to side 1.(more)Hydrostatic pressure is the stress, or pressure, exerted equally in all directions at points within a confined fluid (liquid or gas). It is the only stress possible in a fluid at rest. See Pascal’s principle.
Lithostatic pressure, the stress exerted on a body of rock by surrounding rock, is a pressure in Earth’s crust somewhat analogous to hydrostatic pressure in fluids. Lithostatic pressure increases with depth below Earth’s surface.
This article was most recently revised and updated by Kara Rogers.
PRESSURE Definition & Usage Examples | Dictionary.com
PRESSURE Definition & Usage Examples | Dictionary.com
GamesDaily CrosswordWord PuzzleWord FinderAll gamesFeaturedWord of the DaySynonym of the DayWord of the YearNew wordsLanguage storiesAll featuredPop cultureSlangEmojiMemesAcronymsGender and sexualityAll pop cultureWriting tipsGrammar Coach™Writing hubGrammar essentialsCommonly confusedAll writing tipsGamesFeaturedPop cultureWriting tipspressure[ presh-er ]show ipaSee synonyms for: pressurepressuredpressurespressuring on Thesaurus.comnounthe exertion of force upon a surface by an object, fluid, etc., in contact with it: the pressure of earth against a wall.Physics. force per unit area. Symbol: P: Compare stress (def. 6). Meteorology. atmospheric pressure. Electricity. electromotive force. the state of being pressed or compressed. harassment; oppression: the pressures of daily life.a constraining or compelling force or influence: the social pressures of city life;financial pressure.urgency, as of affairs or business: He works well under pressure.Obsolete. that which is impressed.See moreverb (used with object),pres·sured, pres·sur·ing.to force (someone) toward a particular end; influence: They pressured him into accepting the contract.pressurize. Origin of pressure1First recorded in 1350–1400; Middle English (noun), from Latin pressūra; see press1, -ureOther words from pressurepres·sure·less, adjectivein·ter·pres·sure, adjectivenon·pres·sure, noun, adverbsu·per·pres·sure, noun, adjectiveun·der·pres·sure, nounun·pres·sured, adjectiveWords Nearby pressurepress studpress the fleshpress timepresstitutepress-uppressurepressure altimeterpressure altitudepressure cabinpressure centerpressure-cookDictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024How to use pressure in a sentenceHowever, according to Brindis, “The pressure has not met the threat in terms of magnitude.”What wildfires in Brazil, Siberia, and the US West have in common | Lili Pike | September 17, 2020 | VoxThe pressure is on for Democrats and Republicans to find a solution before Congress breaks in October.Why lawmakers may choose a more targeted approach for the second round of COVID stimulus | Aric Jenkins | September 16, 2020 | FortuneHere’s a building block that is currently under a lot of pressure, as channels are shifting after the pandemic.How would an SEO agency be built today? Part 2: Current business model(s) | Sponsored Content: SEOmonitor | September 16, 2020 | Search Engine LandWith pressure from the Gang Commission’s ad hoc committee headed by Genevieve Jones-Wright, Stephan went on record stating 332 names were removed from her office’s injunctions.While We’re Rethinking Policing, It’s Time to End Gang Injunctions | Jamie Wilson | September 15, 2020 | Voice of San DiegoThe aforementioned Kaiser poll found that 61% of Americans are worried the FDA will rush to approve a vaccine due to political pressure.6 questions that must be answered in the race for a vaccine | jakemeth | September 15, 2020 | FortuneAre you seeing more commercial pressure from academic presses for historians to sexy it up a bit?Thank Congress, Not LBJ for Great Society | Julian Zelizer, Scott Porch | January 4, 2015 | THE DAILY BEASTLike Sony Entertainment's The Interview, political pressure delayed the arrivale of foreign films in Korea.Propaganda, Protest, and Poisonous Vipers: The Cinema War in Korea | Rich Goldstein | December 30, 2014 | THE DAILY BEASTThe 2014 midterm elections are just months behind us, but already Flake feels the pressure of the 2016 presidential elections.Can This Republican Bring the GOP Back to Its Senses on Immigration? | Tim Mak | December 29, 2014 | THE DAILY BEASTTherefore, some Democrats are under pressure to take policy actions their union allies oppose.How Public Sector Unions Divide the Democrats | Daniel DiSalvo | December 29, 2014 | THE DAILY BEASTDoes any of that come from being attuned to the pressure of that need to entertain?Daphne Merkin on Lena Dunham, Book Criticism, and Self-Examination | Mindy Farabee | December 26, 2014 | THE DAILY BEASTHe held it, but it was without pressure; without recognizance of the delight with which he once grasped it.The Pastor's Fire-side Vol. 3 of 4 | Jane PorterUnder the internal pressure his whiskers stood on end and his face grew red.The Bondboy | George W. (George Washington) OgdenWith him one is at high pressure all the time, and I have gained a good many more ideas from him than I can work up in a hurry.Music-Study in Germany | Amy FayMr. Brown seizes the proffered member, and gives it as hearty a pressure as the publicity of the occasion will permit.Physiology of The Opera | John H. Swaby (AKA "Scrici")This may be done by taking the humming tone and bringing to bear upon it a strong pressure of energy.Expressive Voice Culture | Jessie Eldridge SouthwickSee More ExamplesBritish Dictionary definitions for pressurepressure/ (ˈprɛʃə) /nounthe state of pressing or being pressedthe exertion of force by one body on the surface of anothera moral force that compels: to bring pressure to bearan urgent claim or demand or series of urgent claims or demands: to work under pressurea burdensome condition that is hard to bear: the pressure of griefthe normal force applied to a unit area of a surface, usually measured in pascals (newtons per square metre), millibars, torr, or atmospheres: Symbol: p, Pshort for atmospheric pressure, blood pressureSee moreverb(tr) to constrain or compel, as by the application of moral forceanother word for pressurizeOrigin of pressure1C14: from Late Latin pressūra a pressing, from Latin premere to pressDerived forms of pressurepressureless, adjectiveCollins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012Scientific definitions for pressurepressure[ prĕsh′ər ]The force per unit area that one region of a gas, liquid, or solid exerts on another. Pressure is usually measured in Pascal units, atmospheres, or pounds per square inch.♦ A substance is said to have negative pressure if some other substance exerts more force per unit area on it than vice versa. Its value is simply the negative of the pressure exerted by the other substance.The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Cultural definitions for pressurepressureThe force exerted on a given area. (See atmospheric pressure.)Notes for pressureThe most familiar measure of pressure is psi (pounds per square inch), used to rate pressure in automobile and bicycle tires.The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Browse#aabbccddeeffgghhiijjkkllmmnnooppqqrrssttuuvvwwxxyyzzAboutCareersShopContact usAdvertise with usCookies, terms, & privacyDo not sell my infoFollow usGet the Word of the Day every day!Sign upBy clicking "Sign Up", you are accepting Dictionary.com Terms & Conditions and Privacy Policies.My account© 2024 Dictionary.com, LLC