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Other units of pressure, such as pounds per square inch (lbf/in 2) and bar, are also in common use. The CGS unit of pressure is the barye (Ba), equal to 1 dyn·cm −2, or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre ("g/cm 2" or "kg/cm 2") and the like without properly identifying the force ...
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface. Right: The reduction in flux passing through a surface can be visualized by reduction in F or d S equivalently (resolved into components , θ is angle to ...
The pound per square inch (abbreviation: psi) or, more accurately, pound-force per square inch (symbol: lbf/in 2), [1] is a unit of measurement of pressure or of stress based on avoirdupois units and used primarily in the United States. It is the pressure resulting from a force with magnitude of one pound-force applied to an area of one square ...
Units for other physical quantities are derived from this set as needed. In English Engineering Units, the pound-mass and the pound-force are distinct base units, and Newton's Second Law of Motion takes the form = where is the acceleration in ft/s 2 and g c = 32.174 lb·ft/(lbf·s 2).
Isotherms of an ideal gas for different temperatures. The curved lines are rectangular hyperbolae of the form y = a/x. They represent the relationship between pressure (on the vertical axis) and volume (on the horizontal axis) for an ideal gas at different temperatures: lines that are farther away from the origin (that is, lines that are nearer to the top right-hand corner of the diagram ...
The SI unit of dynamic viscosity is the newton-second per square meter (N·s/m 2), also frequently expressed in the equivalent forms pascal-second (Pa·s), kilogram per meter per second (kg·m −1 ·s −1) and poiseuille (Pl). The CGS unit is the poise (P, or g·cm −1 ·s −1 = 0.1 Pa·s), [28] named after Jean Léonard Marie Poiseuille.
The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and has largely replaced the pounds per square inch (psi) unit, except in some countries that still use the imperial measurement system or the US customary system, including the United States.
where (in SI units): q is the dynamic pressure in pascals (i.e., N/m 2, ρ (Greek letter rho) is the fluid mass density (e.g. in kg/m 3), and; u is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume. For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and ...