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At 0 °C (32 °F), the speed of sound in dry air (sea level 14.7 psi) is about 331 m/s (1,086 ft/s; 1,192 km/h; 740 mph; 643 kn). [1] The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in dry air, deviating slightly from ideal behavior.
(mph) (km/h) (m/s) Subsonic <0.8 <530 <609 <980 <273 Most often propeller-driven and commercial turbofan aircraft with high aspect-ratio (slender) wings, and rounded features like the nose and leading edges. The subsonic speed range is that range of speeds within which, all of the airflow over an aircraft is less than Mach 1.
Wind speed Wave height Sea conditions Land conditions Sea conditions (photo) Associated warning flag 0 Calm < 1 knot < 1 mph < 1 km/h 0–0.2 m/s: 0 ft 0 m Sea like a mirror Smoke rises vertically 1 Light air 1–3 knots 1–3 mph 1–5 km/h 0.3–1.5 m/s 0–1 ft 0–0.3 m Ripples with appearance of scales are formed, without foam crests
Hull speed or displacement speed is the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel. As boat speed increases from rest, the wavelength of the bow wave increases, and usually its crest-to-trough dimension (height) increases as well. When hull speed is exceeded, a vessel in displacement mode ...
Speed (m/s) Momentum (N⋅s) Explanation 0.42 2.4 1 A 420-gram (15 oz) football (FIFA specified weight for outdoor size 5) kicked to a speed of 8.6 km/h (5.3 mph). 0.42 38 16 The momentum of the famous football kick of the Brazilian player Roberto Carlos in the match against France in 1997. The football had a speed of 137 km/h (85 mph), making ...
A wind speed gradient of 4 (m/s)/km can produce refraction equal to a typical temperature lapse rate of 7.5 °C/km. [51] Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, [52] eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind.
If the wave is a sound wave and the sound source is moving faster than the speed of sound, the resulting shock wave creates a sonic boom. Lord Rayleigh predicted the following effect in his classic book on sound: if the observer were moving from the (stationary) source at twice the speed of sound, a musical piece previously emitted by that ...
For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.