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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 Austrian physicist and philosopher Ernst Mach. where: M is the local Mach number, u is the local flow velocity ...
Speed of sound. 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.
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h). Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic.
The supersonic speed range is that range of speeds within which all of the airflow over an aircraft is supersonic (more than Mach 1). But airflow meeting the leading edges is initially decelerated, so the free stream speed must be slightly greater than Mach 1 to ensure that all of the flow over the aircraft is supersonic.
Supersonic aircraft are any aircraft that can achieve flight faster than Mach 1, which refers to the speed of sound. "Supersonic includes speeds up to five times Mach than the speed of sound, or Mach 5." (Dunbar, 2015) The top mileage per hour for a supersonic aircraft normally ranges from 700 to 1,500 miles per hour (1,100 to 2,400 km/h).
The Mach–Zehnder interferometeris named after his son Ludwig Mach, who was also a physicist. Ernst Waldfried Josef Wenzel Mach(/mɑːx/MAHKH; German:[ɛʁnstˈmax]; 18 February 1838 – 19 February 1916) was an Austrian physicistand philosopher, who contributed to the physics of shock waves. The ratio of the speed of a flow or object to that ...
FM radio channel assignments in the U.S. In the United States, FM broadcasting stations operate on a 20.2 MHz-wide frequency band, spanning from 87.8 MHz to 108 MHz. This is divided into 101 0.2 MHz-wide channels, which are designated as channels 200 through 300. In actual practice, few except the FCC use these channel numbers; the frequencies ...
The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft 's drag at transonic speeds which occur between about Mach 0.75 and 1.2. For supersonic speeds a different procedure called the supersonic area rule, developed by NACA aerodynamicist Robert ...