WordNet
n. a unit of pressure [syn: psi]
Wikipedia
The pound per square inch or, more accurately, pound-force per square inch (abbreviations: psi, lbf/in, lb/in, lbf/sq in, lb/sq in) is a unit of pressure or of stress based on avoirdupois units. It is the pressure resulting from a force of one pound-force applied to an area of one square inch:
1 psi = $\frac{1\text{ lbf}}{(1\text{ in})^2}$ ≈ $\frac{4.4482\text{ N}}{(0.0254\text{ m})^2}$ ≈ 6894.757 N/m²
Therefore, one pound per square inch is approximately 6894.757 Pa.
Now converting the psi to standard atmospheres:
1 atm = 101325Pa = $\frac{101325}{6894.757293168}$ ≈ 14.70 psi
Therefore, 1 atmosphere is approximately 14.7 pounds per square inch.
Pounds per square inch absolute (psia) is used to make it clear that the pressure is relative to a vacuum rather than the ambient atmospheric pressure. Since atmospheric pressure at sea level is around 14.7 psi, this will be added to any pressure reading made in air at sea level. The converse is pounds per square inch gauge or pounds per square inch gage (psig), indicating that the pressure is relative to atmospheric pressure. For example, a bicycle tire pumped up to 65 psi above local atmospheric pressure (say, 14.7 psia locally), will have a pressure of 65 + 14.7 = 79.7 psia or 65 psig. When gauge pressure is referenced to something other than ambient atmospheric pressure, then the units would be pounds per square inch differential (psid).
Usage examples of "pounds per square inch".
That's water being blown from the ballast tanks by high pressure air - something like three thousand pounds per square inch.
At half of fifteen pounds per square inch, and allowing for the arch of the roof, that's a load of one and an eighth billion pounds.
The suit, pressurized at three and a half pounds per square inch, was like a balloon around her, and it kept her body stiff, like a manikin, and she couldn't save herself.
A typical tire with a maximum recommended pressure of 32 pounds per square inch has a safe pressure range of 24-32 PSI.
The car held up under fifteen pounds per square inch pressure differential applied from outside.
The pressure of the sea increases at the rate of fifteen pounds per square inch for every thirty feet.
He winced again when his mental gymnastics gave him an approximate answer of nearly 6200 pounds per square inch, the pressure which at that moment was pushing against the red paint on the Sappho I's thick titanium skin.
Although the pressure at that depth was nearly 17,000 pounds per square inch, they noticed with surprise that they disturbed a bottom-dwelling flatfish just as they touched down.
There, some seven miles down, the pressures rise to over sixteen thousand pounds per square inch.
The astronaut was helped into his full pressure suit, with his biosensors attached and his rectal thermometer inserted, and then placed into the gondola, in a contoured seat molded for his body, whereupon all the wires, hoses, and microphones he would have in actual flight were hooked up, and the gondola was depressurized to five pounds per square inch, as it would be in space flight.
The fifteen pounds per square inch around you includes three pounds of oxygen pressure.
Three pressure-pounds per square inch means nine mass pounds, because Ganymede has only one third the surface gravitation of Earth.