pascal unit
Details:
The pascal is the unit of pressure under the SI/metric system. “Pressure” refers to force exerted over area, and the term is used in medicine (blood pressure), meteorology (air pressure), fluid dynamics (static or stagnation pressure), and many other fields.
Traditional measures of pressure drew on those developed by Torricelli and [named after] Blaise Pascal* in the 1640’s, and involved measuring the height of a column of water or mercury.
Although it was Torricelli who initially observed that air pressure changed over different altitudes, it was Pascal who saw the potential for weather forecasting, studied the behavior of other fluids under pressure, and designed a hydraulic press.
Many different measures of pressure still exist, including the bar, the pound-force per square-inch (or PSI), and inches (or centimeters) of mercury. In 1971, the General Conference on Weights and Measures—the world body responsible for the SI/metric system—paid tribute to Pascal by naming the basic unit of pressure after him, and defined it to equal the force of 1 newton exerted over 1 square metre.
Oneliner: The pascal
Bibliography:
- George F. Simmonds, “Calculus with Analytic Geometry”, pp.797 – 800, McGraw-Hill, 1985
- James Burke, “Connections”, pp. 74 – 5, Macmillan London, 1978
- Bureau Internationale des Poids et Mesures website, summary of the resolutions of the 14th General conference, http://www.bipm.org/en/convention/cgpm/14/pascal-siemens.html
- “Pressure”, Wikipedia, http://en.wikipedia.org/wiki/Pressure#Units