Pressure is the ratio of force applied per area covered …
| P = | F |
| A |
The unit of pressure is the pascal
| ⎡ ⎣ |
Pa = | N | = | kg m/s2 | = | kg | ⎤ ⎦ |
| m2 | m2 | m s2 |
The pascal is also a unit of stress and the topics of pressure and stress are connected.
spring loaded pressure gauge
| atm | kPa | device, event, phenomena, process |
|---|---|---|
| 200 | 20,000 | pressurized breathing apparatus |
| 150 | 15,000 | milk homogenization |
| 110 | 11,000 | rupture compression strength of vertebral disks |
| 7–14 | 700–1400 | puffed cereal manufacture |
| 9 | 900 | espresso machine |
| 4–7 | 400–700 | bicycle tire |
| > 4 | > 400 | oxygen poisoning and nitrogen narcosis for dives > 30 m |
| 2.7–4.1 | 275–415 | champagne at serving temperature (10 ℃) |
| 2.7 | 275 | carbonated soft drinks |
| 2.0–2.5 | 200–250 | car tire |
| > 4 | > 400 | blast wave, 100% lethality |
| 2.3–4.0 | 230–400 | blast wave, 50% lethality |
| 1.6–2.3 | 160–230 | blast wave, 1% lethality |
| 1.02 | 103 | typical household pressure cooker |
| 1 | 101.325 | one standard atmosphere over environment |
| 47 | bottom of feet while standing | |
| 20 | lungs, extreme exhalation | |
| 17 | sustained pressure, eardrum ruptures | |
| 8 | sustained pressure, eardrum senses pain | |
| 13–19 | blood pressure, arterial, systolic (during a heartbeat) | |
| 8–12 | blood pressure, arterial, diastolic (between heartbeats) | |
| 7–14 | aircraft shock wave | |
| 8.8 | blowing your nose | |
| 11 | eye, severe glaucoma | |
| 1.6–3.0 | eye, normal | |
| 4.0 | blood pressure, capillary, arterial end | |
| 1.3 | blood pressure, capillary, venous end | |
| 15 | bladder, voiding, maximum | |
| 3 | bladder, micturition reflex ("gotta go urge") | |
| 2–4 | bladder, voiding, sustained | |
| 1.3–2.6 | gastrointestinal tract | |
| 0.6–1.6 | cerebrospinal fluid | |
| 0.4–0.9 | blood pressure, venous | |
| 0.6–0.8 | interstitial fluid (osmotic pressure) | |
| 2 | acoustic pressure, eardrum ruptures (160 dB) | |
| 0.02 | acoustic pressure, eardrum senses pain (120 dB) | |
| 2 × 10−8 | acoustic pressure, threshold of hearing (0 dB) | |
| 0 | 0 | environmental pressure |
| −1.3 | lungs, resting | |
| −1.5 | lungs, drinking through a 15 cm straw | |
| −25 | lungs, extreme inhalation | |
| −1 |
−101.325 |
one standard atmosphere below environment a perfect vacuum in a standard atmosphere environment |
| atm | Pa | device, event, location, phenomena, process |
|---|---|---|
| 3.4 × 1011 | center of the sun | |
| ???? | center of Jupiter | |
| 3.6 × 106 | center of earth | |
| 1070 | Marianas Trench, Pacific Ocean (-10,924 m) | |
| 160 | Lake Baikal, Asia (-1620 m) | |
| 140 | Lake Tanganyika, Africa (-1470 m) | |
| 40 | Lake Superior, North America (-406 m) | |
| ???? | record dive by a human | |
| 90 | surface of Venus | |
| 26 | helium freezes at about 1 K | |
| > 5 | oxygen poisoning and nitrogen narcosis for dives > 30 m | |
| 108,380 | record high, altitude adjusted (Siberia, 1968) | |
| 106,000 | dead sea (-400 m) | |
| 1 | 101,325 | sea level, standard atmosphere |
| 90,000 | atmospheric pressure at 1000 m, interior of concorde | |
| 88,800 | record low, altitude adjusted (Hurricane Gilbert, 1988) | |
| 80,000 | atmospheric pressure at 2000 m, interior of typical jet aircraft | |
| 52,000 | La Paz, Bolivia (5200 m) | |
| ~ ½ | 51,000 | maximum altitude of permanent human habitation (5500 m) |
| ~ 40,000 ~ | vertical limit of human survivability (~7000 m) | |
| ~ ⅓ | 31,000 | Mount Everest (8848 m) |
| ~ ⅕ | 19,000 | altitude of typical commercial jet aircraft (12,000 m) |
| 0.062 | 6,3000 | Armstrong limit, exposed body liquids boil (19,000 m) |
| > 0.033 | > 3,300 > | "low vacuum" |
| < 0.033 | < 3,300 < | "medium vacuum" |
| 0.025 | 2,200 | altitude of reconnaissance plane (SR-71, 26,000 m) |
| 0.011 | 1,100 | altitude of highest skydive (1960, 31,330 m) |
| 0.006 | 600 | altitude of highest manned balloon flight (1961, 34,668 m) |
| 0.007 | surface of Mars | |
| ~ 10−5 | surface of Pluto, maximum (late 1990s) | |
| < 10−6 | "high vacuum" | |
| < 10−9 | "very high vacuum" | |
| ~ 10−13 | surface of the moon, daytime | |
| < 10−12 | "ultra high vacuum" | |
| ~ 10−15 | surface of the moon, nighttime | |
| < 10−15 | "extreme ultrahigh vacuum" | |
| ~ 10−17 | I am told that below this value all vacuum equipment leaks. |
Standard Atmospheric Tables
| gas | formula | molecular weight (g/mol) |
fraction |
|---|---|---|---|
| nitrogen | N2 | 028.0134000 | 0.78084 |
| oxygen | O2 | 031.9988000 | 0.209476 |
| argon | Ar | 039.9480000 | 0.00934 |
| carbon dioxide | CO2 | 044.0099500 | 0.000314 |
| neon | Ne | 020.1830000 | 0.00001818 |
| helium | He | 004.0026000 | 0.00000524 |
| methane | CH4 | 016.0430300 | 0.000002 |
| krypton | Kr | 083.8000000 | 0.00000114 |
| hydrogen | H2 | 002.0159400 | 0.0000005 |
| xenon | Xe | 131.3000000 | 0.000000087 |
| overall | – | 028.9644253 | 0.999997147 |
| Source: | US Standard Atmosphere, 1976 |
Pressure in a uniform fluid.
The absolute pressure in a uniform fluid at a particular depth is given by …
P = P0 + ρgh
The absolute pressure in a uniform or nonuniform fluid at a particular depth h measured along the vertical or z-axis is given by …
| h | ||
| P = P0 + | ⌠ ⌡ | ρ(z)g(z) dz |
| 0 | ||
barometer
barometer, manometer, Hare's apparatus
The atmosphere as a unit.
| 1 atm | = | 101,325 Pa | (by definition) |
| = | 760 torr | (by definition) | |
| = | 763.43… mm Hg | (approximately) | |
| = | 1.03… kg/cm2 | (approximately) | |
| = | 10.3… tonnes/m2 | (approximately) | |
| = | 14.7… psi | (approximately) | |
| = | 1.06… tons/ft2 | (approximately) |
blood pressure
ear pressure in the middle ear: eardrum at end of outer ear connected to smaller oval window at beginning of inner ear. 15-30 times greater pressure. combination of difference in membrane diameters and lever effects of middle ear bones.
eye pressure and glaucoma
| location | systolic | diastolic | mean |
|---|---|---|---|
| aorta | 120 | 80 | 100 |
| left ventricle | 120 | 8 | – |
| left atrium | 7 | 10 | 4 |
| pulmonay artery | 15 | 7 | 12 |
| right ventricle | 15 | 2 | – |
| right atrium | 4 | 4 | 0 |
| pulmonary capillary wedge | 7 | 10 | 4 |
| Source: | Physics of the Body |
Pascal's principle: Pressure changes applied to the surface of an enclosed fluid are transmitted evenly throughout the fluid.
hydraulics
Queckenstedt's maneuver - barbaric medical test from the early 20th Century to test for spinal stenosis
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The Physics Hypertextbook © 1998–2013 Glenn Elert |
No condition is permanent.