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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.
Average walking speed—below a speed of about 2 m/s, it is more efficient to walk than to run, but above that speed, it is more efficient to run. 2.39: 8.53: 5.35: 7.97 × 10 −9: World record time 50m freestyle swim 5.78: 20.81: 12.93: 1.928 × 10 −8: World record time marathon [13] 6–7: 20–25: 12–15: 1.8–2.3 × 10 −8 ...
The usual nomenclature of ammunition indicates the diameter of projectile and the length of the cartridge that holds it; for example, 20×102 mm is a 20 mm projectile in a 102 mm long case. Though this designation is often assumed to be unique, this is not always the case, e.g. there are three different 20×110 mm types which are not compatible.
Speed; system unit code (alternative) symbol or abbrev. notes sample default conversion combinations SI: metre per second: m/s m/s US spelling: meter per second: 1.0 m/s (3.3 ft/s) m/s ft/s (m/s foot/s) non-SI metric: kilometre per hour: km/h km/h US spelling: kilometer per hour: 1.0 km/h (0.62 mph) km/h mph; Imperial & US customary: mile per ...
The first GE prototypes of the 0.60-inch (15 mm) caliber T45 were ground-fired in 1949; it achieved 2,500 rpm, which was increased to 4,000 rpm by 1950. By the early 1950s, the USAF decided that high velocity alone might not be sufficient to ensure target destruction and tested 20 and 27 mm (0.787 and 1.06 in) alternatives based on the 0.60 ...
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While these speeds are fine for small router bits, using larger bits, say more than 1-inch (25 mm) or 25 millimeters in diameter, can be dangerous and can lead to chatter. Larger routers now have variable speeds and larger bits require slower speed. Drilling wood generally uses higher spindle speeds than metal, and the speed is not as critical ...
Airspeed is commonly given in knots (kn). Since 2010, the International Civil Aviation Organization (ICAO) recommends using kilometers per hour (km/h) for airspeed (and meters per second for wind speed on runways), but allows using the de facto standard of knots, and has no set date on when to stop.