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The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10 −2 metres ( 1 / 100 m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimeters; 1 cm – 0.39 inches; 1 cm – edge of a square of area 1 cm 2
One barn is equal to 1.0 × 10 −28 m 2. The name derives from the folk expressions "As big as a barn," and "Couldn't hit the broad side of a barn", used by particle accelerator physicists to refer to the probability of achieving a collision between particles. For nuclear purposes, 1.0 × 10 −28 m 2 is actually rather large. [25]
Multiples and submultiples of metric units are related by powers of ten and their names are formed with prefixes. This relationship is compatible with the decimal system of numbers and it contributes greatly to the convenience of metric units. In the early metric system there were two base units, the metre for length and the gram for mass. The ...
In the past, a common time measuring instrument was the sundial. Today, the usual measuring instruments for time are clocks and watches. For highly accurate measurement of time an atomic clock is used. Stopwatches are also used to measure time in some sports.
A variety of rulers A carpenter's rule Retractable flexible rule or tape measure A closeup of a steel ruler A ruler in combination with a letter scale. A ruler, sometimes called a rule, scale or a line gauge or metre/meter stick, is an instrument used to make length measurements, whereby a length is read from a series of markings called "rules" along an edge of the device. [1]
In radio astronomy, the unit of electromagnetic flux is the jansky (symbol Jy), equivalent to 10 −26 watts per square metre per hertz (= 10 −26 kg/s 2 in base units, about 8.8×10 −31 BTU/ft 2). It is named after the pioneering radio astronomer Karl Jansky. The brightest natural radio sources have flux densities of the order of one to one ...
The shed is a unit of area used in nuclear physics equal to 10 −24 barns (100 rm 2 = 10 −52 m 2). The outhouse is a unit of area used in nuclear physics equal to 10 −6 barns (100 am 2 = 10 −34 m 2). The barn (b) is a unit of area used in nuclear physics equal to one hundred femtometres squared (100 fm 2 = 10 −28 m 2).
The millimetre (mm), centimetre (cm) and the kilometre (km), derived from the metre, are also commonly used units. In U.S. customary units, English or imperial system of units, commonly used units of length are the inch (in), the foot (ft), the yard (yd), and the mile (mi).