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Here the metric prefix 'kilo-' (symbol 'k') stands for a factor of 1000; thus, 1 km = 1000 m. The SI provides twenty-four metric prefixes that signify decimal powers ranging from 10 −30 to 10 30, the most recent being adopted in 2022.
When units occur in exponentiation, such as in square and cubic forms, any multiplier prefix is considered part of the unit, and thus included in the exponentiation. 1 km 2 means one square kilometre or the area of a square that measures 1000 m on each side or 10 6 m 2 (as opposed to 1000 square meters, which is the area of a square that ...
The units kilogram, gram, milligram, microgram, and smaller are commonly used for measurement of mass. However, megagram, gigagram, and larger are rarely used; tonnes (and kilotonnes, megatonnes, etc.) or scientific notation are used instead. The megagram does not share the risk of confusion that the tonne has with other units with the name "ton".
The SI prefix for a thousand units is "kilo-", abbreviated to "k"—for instance, a kilogram or "kg" is a thousand grams. This is sometimes extended to non-SI contexts, such as "ka" being used as a shorthand for periods of 1000 years. In computer science, however, "kilo-" is used more loosely to mean 2 to the 10th power (1024).
The unit prefixes are always considered to be part of the unit, so that, e.g., in exponentiation, 1 km 2 means one square kilometre, not one thousand square metres, and 1 cm 3 means one cubic centimetre, not one hundredth of a cubic metre. In general, prefixes are used with any metric unit, but may also be used with non-metric units.
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 are (a) is a unit of area equal to 100 m 2. The decare (daa) is a unit of area equal to 1000 m 2.
Many compound units for various kinds of rates explicitly mention units of time to indicate a change over time. For example: miles per hour, kilometres per hour, dollars per hour. Power units, such as kW, already measure the rate of energy per unit time (kW=kJ/s). Kilowatt-hours are a product of power and time, not a rate of change of power ...
K: Θ: thermodynamic temperature: The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380 649 × 10 −23 J⋅K −1, (J = kg⋅m 2 ⋅s −2), given the definition of the kilogram, the metre, and the second. K: SI: Physics: Basic: mole: mol: N: amount of substance: The amount of substance of exactly 6. ...