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Comparison of 1 square metre with some Imperial and metric units of area. The square metre (international spelling as used by the International Bureau of Weights and Measures) or square meter (American spelling) is the unit of area in the International System of Units (SI) with symbol m 2. [1]
[4]: 2 For example, using meters per second is coherent in a system that uses meter for length and seconds for time, but kilometre per hour is not coherent. The principle of coherence was successfully used to define a number of units of measure based on the CGS, including the erg for energy , the dyne for force , the barye for pressure , the ...
where Pd is the power density in watts per square meter (one W/m 2 is equal to 0.1 mW/cm 2), H 2 = the square of the value of the magnetic field in amperes RMS squared per meter squared, E 2 = the square of the value of the electric field in volts RMS squared per meter squared. [6]
One newton equals one kilogram metre per second squared. Therefore, the unit metre per second squared is equivalent to newton per kilogram, N·kg −1, or N/kg. [2] Thus, the Earth's gravitational field (near ground level) can be quoted as 9.8 metres per second squared, or the equivalent 9.8 N/kg.
M 2 is useful because it reflects how well a collimated laser beam can be focused to a small spot, or how well a divergent laser source can be collimated. It is a better guide to beam quality than Gaussian appearance because there are many cases in which a beam can look Gaussian, yet have an M 2 value far from unity. [1]
The SI has special names for 22 of these coherent derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m 2), the SI derived unit of area; and the kilogram per cubic metre (kg/m 3 or kg⋅m −3), the SI derived unit of density.
The American football field, which has a playing area 100 yards (91.4 m) long by 160 feet (48.8 m) wide. This is often used by the American public media for the sizes of large buildings or parks. It is used both as a unit of length (100 yd or 91.4 m, the length of the playing field excluding goal areas) and as a unit of area (57,600 sq ft or ...
Square foot: sq ft or ft 2: 0.09290 m 2: Square yard: sq yd or yd 2: 9 sq ft 0.8361 m 2: Acre UK: 4840 sq yd 4046 m 2: Notes. Land area in the US Unit Abbreviation