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The word ton or tonne is derived from the Old English tunne, and ultimately from the Old French tonne, and referred originally to a large cask with a capacity of 252 wine gallons, which holds approximately 2100 pounds of water. Such a barrel (of any similar volume) is still called a tun in British English, but this usage is dying out.
The modern spelling tonne, almost always referring to the metric ton of 1000 kilograms (or the associated obsolete force unit) when used in English, is a direct borrowing from the French language.
There are a ton of tons:
Units of mass
There are three similar units of mass called the ton or tonne: - tonne or metric ton = 1000 kg (2204.6 lb). The official symbol is t, but mT, MT, and T are also used. This is not an SI unit, though it is acceptable for use with SI. The name for this unit in SI is the megagram (symbol: Mg).
- short ton (or simply ton in casual use in the USA) = 907.185 kg (2000 lb).
- long ton (or weight ton) = 1016.047 kg (2240 lb), was commonly used in the UK (before it adopted the 1000 kg tonne) and for petroleum products. It is also used in the U.S., as in many other countries, for things such as the deadweight tonnage of naval ships.
As a displacement ton the long ton is normally measured as the mass of 35 cubic feet of sea water. Increasingly, metric tons are being used rather than long tons in measuring the displacement of ships.
Both the short ton and the long ton are composed of twenty hundredweights, each having different values for the hundredweight (100 and 112 pounds respectively). Prior to the 15th century in England, the ton was still composed of twenty hundredweights, but each was 108 lb, giving a ton of 2160 pounds.
In the context of nuclear power plants, tHM and MTHM mean (metric) tons of heavy metal, and MTU means metric tons uranium.
Units of force There are also the units of force based on each of these three mass units. However, it is only the metric ton or tonne as a unit of mass which is acceptable for use with SI. The metric tonne force (tonne force), like the kilogram force, is not acceptable for use with SI. - 1 short ton force = 2000 lbf = 8.89644 kilonewtons (kN)
- 1 long ton force = 2240 lbf = 9.96402 kN
- 1 metric ton force = 1000 kgf = 9.80665 kN
Units of volume The freight ton or measurement ton is a unit of volume used for describing ship capacities (tonnage) or cargo. One measurement ton is equal to: The amount of fresh water at 4 °C displaced by one measurement ton has a mass similar to the ton masses listed above: 1133 kg, or 2497 lb. The measurement ton is abbreviated as M/T, MT, or MTON, which can cause it to be confused with the metric ton.
The register ton is also a unit of volume, defined as 100 cubic feet. It is often abbreviated GRT for gross registered ton.
See 1 E-1 mł and orders of magnitude (volume) for a comparison with other volumes.
Units of energy and power In refrigeration and air-conditioning, a refrigeration ton can be - A unit of power equal to 12,000 Btu/h = 3.516853 kilowatts (kW)
- A corresponding unit of energy equal to that power over a period of a day, or 24 × 12,000 Btu = 288,000 Btu = 303.856 megajoules (MJ)
- A ton of TNT or tonne of TNT is equal to 1,000,000 grams at a conventional energy value of 1000 small calories per gram, thus 1 gigacalorie, or 4.184 gigajoules. See also megaton.
- A tonne of oil equivalent. See, e.g., Gtoe.
Miscellaneous tons - Ton is also used informally to mean a large amount of something.
- Units of speed: in slang or informal usage, a ton can be
- In money, a ton is slang for 100 GBP (pounds sterling) - this is primarily used in London, England.
- In darts, a ton is a score of 100 or more points with three darts.
- In motor vehicles, many trucks are classified into groups loosely related to their carrying capacity as 1/2 ton, 3/4 ton, 2 1/2 ton (deuce-and-a-half in U.S. military slang), 5 ton, etc.
See also
External links - Conversion calculator for units of mass (Cleave Books) (http://www.ex.ac.uk/trol/scol/ccvol.htm)
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