# Recursos presión

Asociado a leyes gases , fuerzas en fluidos.

Se introducen unidades (Pa, atm, bar, mmHg)
Aparte de Pa (pascal), hay otras aceptadas por el SI
https://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf Table 8. Other non-SI units

Quantity Name of unit Symbol for unit Value in SI unit
pressure bar (a) bar 1 bar = 0.1 MPa = 100 kPa = 105 Pa
millimetre of mercury (b) mmHg 1 mmHg ≈ 133.322 Pa

(a) The bar and its symbol are included in Resolution 7 of the 9th CGPM (1948; CR, 70). Since 1982 one bar has been used as the standard pressure for tabulating all thermodynamic data. Prior to 1982 the standard pressure used to be the standard atmosphere, equal to 1.013 25 bar, or 101 325 Pa.
(b) The millimetre of mercury is a legal unit for the measurement of blood pressure in some countries.

https://www.monografias.com/docs111/introduccion-neumatica/introduccion-neumatica.shtml
1/10 bar (10,000 Pa) es aprox. lo más fuerte que una persona promedio puede soplar

### La atmósfera

Una atm son 101325 Pa (en libro de texto reciente veo que indica 101300 Pa, y son 101235 Pa desde 1954)
http://www.bipm.org/en/CGPM/db/10/4/
1 standard atmosphere = 1 013 250 dynes per square centimetre, i.e., 101 325 newtons per square metre.
In 1954, the definition of the atmosphere was revised by the 10e Conférence Générale des Poids et Mesures (10th CGPM)[ https://www.bipm.org/en/CGPM/db/10/4/ ] to the currently accepted definition: one atmosphere is equal to 101325 pascals. The torr was then redefined as 1/760 of one atmosphere. This yields a precise definition that is unambiguous and independent of measurements of the density of mercury or the acceleration due to gravity on Earth.

### Milímetros de mercurio

El símbolo es mmHg según SI: junto, no separado.
Se puede usar torr (nombre torr, símbolo Torr), pero se desaconseja

https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-5-units-outside-si
Table 11. Example of other unacceptable units

Name Symbol Value in SI units
torr Torr 1 Torr = (101 325/760) Pa

https://en.wikipedia.org/wiki/Torr#Nomenclature_and_common_errors
The unit’s name torr is written in lower case, while its symbol (“Torr”) is always written with upper-case initial; including in combinations with prefixes and other unit symbols, as in “mTorr” (millitorr) or “Torr⋅L/s” (torr-litres per second).[2] The symbol (uppercase) should be used with prefix symbols (thus, mTorr and millitorr are correct, but mtorr and milliTorr are not).The torr is sometimes incorrectly denoted by the symbol “T”, which is the SI symbol for the tesla, the unit measuring the strength of a magnetic field. Although frequently encountered, the alternative spelling “Tor” is incorrect.

## Presión estándar

Citado en apuntes de termoquímica de Bachillerato
http://goldbook.iupac.org/html/S/S06036.html
STP
Abbreviation for standard temperature (273.15 K or 0 °C) and pressure (105 Pa); usually employed in reporting gas volumes. Note that flow meters calibrated in standard gas volumes per unit time often refer to volumes at 25 °C, not 0 °C.