Search results
Results from the WOW.Com Content Network
The original is a unit of energy, equal to the energy in one mole (1 mol) of photons. The second is a unit of amount of photons, equal to one mole (1 mol) of photons. The rayleigh (R) is a unit of photon flux rate density equal to 10 10 m −2 ⋅s −1 (10 4 mm −2 ⋅s −1).
The other units of length and mass, and all units of area, volume, and derived units such as density were derived from these two base units. Mesures usuelles (French for customary measures) were a system of measurement introduced as a compromise between the metric system and traditional measurements. It was used in France from 1812 to 1839.
See Weight for detail of mass/weight distinction and conversion. Avoirdupois is a system of mass based on a pound of 16 ounces, while Troy weight is the system of mass where 12 troy ounces equals one troy pound. The symbol g 0 is used to denote standard gravity in order to avoid confusion with the (upright) g symbol for gram.
Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.
The conversion between different SI units for one and the same physical quantity is always through a power of ten. This is why the SI (and metric systems more generally) are called decimal systems of measurement units. [10] The grouping formed by a prefix symbol attached to a unit symbol (e.g. ' km ', ' cm ') constitutes a new inseparable unit ...
The millimetre (SI symbol: mm) is a unit of length in the metric system equal to 10 −3 metres ( 1 / 1 000 m = 0.001 m). To help compare different orders of magnitude , this section lists lengths between 10 −3 m and 10 −2 m (1 mm and 1 cm).
One metre is exactly equivalent to 5 000 / 127 inches and to 1 250 / 1 143 yards. A simple mnemonic to assist with conversion is "three 3s": 1 metre is nearly equivalent to 3 feet 3 + 3 ⁄ 8 inches. This gives an overestimate of 0.125 mm. The ancient Egyptian cubit was about 0.5 m (surviving rods are 523–529 mm). [154]
The ounce (/ ˈ aʊ n s /) is any of several different units of mass, weight, or volume and is derived almost unchanged from the uncia, an Ancient Roman unit of measurement.. The avoirdupois ounce (exactly 28.349523125 g) is 1 ⁄ 16 avoirdupois pound; this is the United States customary and British imperial ounce.