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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    In 1950, Louis Essen determined the speed as 299 792.5 ± 3.0 km/s, using cavity resonance. [112] This value was adopted by the 12th General Assembly of the Radio-Scientific Union in 1957. In 1960, the metre was redefined in terms of the wavelength of a particular spectral line of krypton-86 , and, in 1967, the second was redefined in terms of ...

  3. List of conversion factors - Wikipedia

    en.wikipedia.org/wiki/List_of_conversion_factors

    km/h ≡ 1 km/h = 2. 7 × 10 −1 m/s knot: kn ≡ 1 nmi/h = 1.852 km/h = 0.51 4 m/s knot (Admiralty) kn ≡ 1 NM (Adm)/h = 1.853 184 km/h [29] = 0.514 77 3 m/s mach number: M: Ratio of the speed to the speed of sound [note 1] in the medium (unitless). ≈ 340 m/s in air at sea level ≈ 295 m/s in air at jet altitudes metre per second (SI unit ...

  4. Speed of sound - Wikipedia

    en.wikipedia.org/wiki/Speed_of_sound

    T 25 is 298.15 K (= 25 °C = 77 °F), giving a value of 346.1 m/s (= 1 135.6 ft/s = 1246 km/h = 774.3 mph = 672.8 kn). In fact, assuming an ideal gas , the speed of sound c depends on temperature and composition only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out).

  5. Template:Convert - Wikipedia

    en.wikipedia.org/wiki/Template:Convert

    Converts measurements to other units. Template parameters [Edit template data] This template prefers inline formatting of parameters. Parameter Description Type Status Value 1 The value to convert. Number required From unit 2 The unit for the provided value. Suggested values km2 m2 cm2 mm2 ha sqmi acre sqyd sqft sqin km m cm mm mi yd ft in kg g mg lb oz m/s km/h mph K C F m3 cm3 mm3 L mL cuft ...

  6. Equations for a falling body - Wikipedia

    en.wikipedia.org/wiki/Equations_for_a_falling_body

    Based on wind resistance, for example, the terminal velocity of a skydiver in a belly-to-earth (i.e., face down) free-fall position is about 195 km/h (122 mph or 54 m/s). [3] This velocity is the asymptotic limiting value of the acceleration process, because the effective forces on the body balance each other more and more closely as the ...

  7. Kilometres per hour - Wikipedia

    en.wikipedia.org/wiki/Kilometres_per_hour

    The kilometre, a unit of length, first appeared in English in 1810, [9] and the compound unit of speed "kilometers per hour" was in use in the US by 1866. [10] "Kilometres per hour" did not begin to be abbreviated in print until many years later, with several different abbreviations existing near-contemporaneously.

  8. Speed - Wikipedia

    en.wikipedia.org/wiki/Speed

    The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in vacuum c = 299 792 458 metres per second (approximately 1 079 000 000 km/h or 671 000 000 mph).

  9. Speed of electricity - Wikipedia

    en.wikipedia.org/wiki/Speed_of_electricity

    Free electrons in a conductor follow a random path. Without the presence of an electric field, the electrons have no net velocity. When a DC voltage is applied, the electron drift velocity will increase in speed proportionally to the strength of the electric field. The drift velocity in a 2 mm diameter copper wire in 1 ampere current is ...