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Mach number. The Mach number ( M or Ma ), often only Mach, ( / mɑːk /; German: [max]) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. [ 1][ 2] It is named after the Czech physicist and philosopher Ernst Mach . where: M is the local Mach number, u is the local ...
A scale factor, (conventionally called the speed-of-light) relates distances measured in space to distances measured in time. The magnitude of this scale factor (nearly 300,000 kilometres or 190,000 miles in space being equivalent to one second in time), along with the fact that spacetime is a manifold, implies that at ordinary, non ...
G {\displaystyle G} electrical conductance. siemens (S) universal gravitational constant. newton meter squared per kilogram squared (N⋅m 2 /kg 2 ) shear modulus. pascal (Pa) or newton per square meter (N/m 2 ) g {\displaystyle \mathbf {g} } acceleration due to gravity.
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn ), or 1 km in 2.91 s or one mile in 4.69 s.
Dynamic pressure. In fluid dynamics, dynamic pressure (denoted by q or Q and sometimes called velocity pressure) is the quantity defined by: [1] where (in SI units): 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 ...
Orders of magnitude (pressure) This is a tabulated listing of the orders of magnitude in relation to pressure expressed in pascals. psi values, prefixed with + and -, denote values relative to Earth's sea level standard atmospheric pressure (psig); otherwise, psia is assumed. Magnitude. Pressure. lbf/in 2 or dB.
Dimension. 1 {\displaystyle 1} In geometry, a solid angle (symbol: Ω) is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point. The point from which the object is viewed is called the apex of the solid ...
Hauksbee, who called it the "ratio of refraction", wrote it as a ratio with a fixed numerator, like "10000 to 7451.9" (for urine). [6] Hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1 (water). [7] Young did not use a symbol for the index of refraction, in 1807. In the later years, others started using different symbols: n ...