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The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). [1] It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). [2] The corresponding unit in the International System of Units (SI) is the meter per second.
An international mile is 0.88 data mile. The speed of light is 299,792,458 metres per second (983,571,056 ft/s), or about one foot per nanosecond . If it were exactly one foot per nanosecond, and a target was one data mile away, then the radar return from that target would arrive 12 microseconds after the transmission.
In aviation, the rule of three or "3:1 rule of descent" is a rule of thumb that 3 nautical miles (5.6 km) of travel should be allowed for every 1,000 feet (300 m) of descent. [ 1 ] [ 2 ] For example, a descent from flight level 350 to sea level would require approximately 35x3=105 nautical miles.
0.51444 metres per second (approximately), 1.15078 miles per hour (approximately), 20.25372 inches per second (approximately) 1.68781 feet per second (approximately). The length of the internationally agreed nautical mile is 1 852 m. The US adopted the international definition in 1954, having previously used the US nautical mile (1 853.248 m). [6]
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.
For example, in imperial units, the speed of light is approximately 186 282 miles per second, [Note 3] or roughly 1 foot per nanosecond. [Note 4] [16] [17] In branches of physics in which c appears often, such as in relativity, it is common to use systems of natural units of measurement or the geometrized unit system where c = 1.
In this case, the terminal speed increases to about 90 m/s (300 ft/s), [citation needed] which is almost the terminal speed of the peregrine falcon diving down on its prey. [4] The same terminal speed is reached for a typical .30-06 bullet dropping downwards—when it is returning to the ground having been fired upwards or dropped from a tower ...
To relate radar timing to distances traveled by radar energy, the speed is used to calculate it. With speed of radar waves at approximately the speed of light in vacuum or 299,792,458 metres per second (300 m/μs; 984 ft/μs) and nautical mile at 1,852 metres (6,076 ft), the delay per nautical mile until the wave return is calculated as: