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Definition: pressure from Philip's Encyclopedia

(symbol Pa) In physics, the force on an object's surface divided by the area of the surface. The SI unit is the pascal; 1 pascal is equal to the pressure exerted by a force of 1 newton on an area of 1m2. In meteorology, the millibar (symbol mb), which equals 100 pascals, is commonly used.

pressure

From The Columbia Encyclopedia
in mechanics, ratio of the force acting on a surface to the area of the surface; it is thus distinct from the total force acting on a surface. A force can be applied to and sustained by a single point on a solid. However, a force can only be sustained by the surface of an enclosed fluid, i.e., a liquid or a gas. Thus it is more convenient to describe the forces acting on and within fluids in terms of pressure. Units of pressure are frequently force units divided by area units, e.g., pounds per square inch, dynes per square centimeter, or newtons (N) per square meter. A fluid exerts a pressure on all bodies immersed in it. For a fluid at rest the difference in pressure between two points in it depends only upon the density of the fluid and the difference in depth between the two points. For example, a swimmer diving down in a lake can easily observe an increase in pressure with depth. For each meter (foot) increase in depth, the swimmer is subjected to an increase in pressure of 9,810 N…
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Full text Article pressure

From The Macquarie Dictionary
the exertion of force upon a body by another body in contact with it; compression. Plural: pressures Physics the force per unit area exerted on a given surface. The SI unit of pressure is the pascal. One pascal is equal to one newton per square metre. Plural: pressures Electricity electromotive…
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Full text Article pressure

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
In a fluid, the force exerted normally (at right angles) on the surface of a body immersed in the fluid. The SI unit of pressure is the pascal (Pa), equal to a pressure of one newton per square metre. In the atmosphere, the pressure declines with increasing height from about 100 kPa at sea level to…
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Full text Article pressure

From The Chambers Dictionary
the action of pressing or squeezing; the state of being pressed; impression, stamp ( Shakesp ); constraining force or influence; coercion, forceful persuasion; the need to perform a great deal at speed; tension, strain or stress; ( usu in pl ) a cause of anxiety; urgency; a strong demand; the force…
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Full text Article pressure

From The Columbia Encyclopedia
in mechanics, ratio of the force acting on a surface to the area of the surface; it is thus distinct from the total force acting on a surface. A force can be applied to and sustained by a single point on a solid. However, a force can only be sustained by the surface of an enclosed fluid, i.e., a…
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Full text Article pressure

From Britannica Concise Encyclopedia
Perpendicular force per unit area, or stress at a point within a confined fluid. A solid object exerts pressure on a floor equal to its weight divided by the area of contact. The weight of the Earth’s atmosphere on the surface constitutes atmospheric pressure , which varies from place to place but…
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Full text Article pressure

From The American Heritage(R) Dictionary of the English Language
a. The act of pressing. b. The condition of being pressed. The application of continuous force by one body on another that it is touching; compression. Abbr. P Physics Force applied uniformly over a surface, measured as force per unit area. Meteorology Atmospheric pressure. …
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Full text Article pressure

From The Penguin Dictionary of Physics
Symbol: p. At a point in a fluid, the force exerted per unit area on an infinitesimal plane situated at the point. In a fluid at rest the pressure at any point is the same in all directions. In a liquid it increases uniformly with depth, h , according to the formula: p = ρgh , where ρ is the density…
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Full text Article blood pressure

From The Columbia Encyclopedia
force exerted by the blood upon the walls of the arteries. The pressure in the arteries originates in the pumping action of the heart, and pressure waves can be felt at the wrist and at other points where arteries lie near the surface of the body (see pulse ). Since the heart can pump blood into the…
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Full text Article Blood Pressure

From The Gale Encyclopedia of Senior Health
Blood pressure abnormalities include both high...
Blood pressure refers to pressure against the walls of blood vessels when the heart pumps blood through the arteries, the main oxygen-carrying vessels of the circulatory system. Blood pressure is considered a vital sign (a measurement of a body's basic functioning) and is important to overall health…
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Full text Article Pressure Ulcers

From The Encyclopedia of Aging
Pressure ulcers are the visible evidence of pathological changes in the blood supply to dermal tissues. The chief cause is pressure, or force per unit area, applied to susceptible tissues. Comorbid conditions, especially those resulting in immobility or reducing tissue perfusion, greatly increase…
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