Pressure (the symbol: p) is the ratio of force to the area over which that force is distributed. In other words, pressure is force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure (also spelled gage pressure) is the pressure relative to the local atmospheric or ambient pressure. While pressure may be measured in any unit of force divided by any unit of area, the SI unit of pressure (the newton per square metre) is called the pascal (Pa) after the seventeenth-century philosopher and scientist Blaise Pascal. A pressure of 1 Pa is small; it approximately equals the pressure exerted by a dollar bill resting flat on a table. Everyday pressures are often stated in kilopascals (1 kPa = 1000 Pa).
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Famous quotes containing the word pressure:
“Adolescence is when girls experience social pressure to put aside their authentic selves and to display only a small portion of their gifts.”
—Mary Pipher (20th century)
“This is a catastrophic universe, always; and subject to sudden reversals, upheavals, changes, cataclysms, with joy never anything but the song of substance under pressure forced into new forms and shapes.”
—Doris Lessing (b. 1919)
“Destiny is an absolutely definite and inexorable ruler. Physical ability and moral determination count for nothing. It is impossible to perform the simplest act when the gods say “no.” I have no idea how they bring pressure to bear on such occasions; I only know that it is irresistible.”
—Aleister Crowley (1875–1947)