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词条 Tonne
释义

  1. Symbol and abbreviations

  2. Origin and spelling

  3. Conversions

  4. Derived units

  5. Alternative usage

     Unit of force 

  6. See also

  7. Notes and references

  8. External links

{{Infobox unit
| bgcolor =
| name = Tonne
| image = Illustration of One Tonne 2018.07.06.png
| caption = One tonne is equal to 1000 kilograms or 1 megagram
| standard = Non-SI unit accepted for use with SI
| quantity = Mass
| symbol = t
| extralabel = In SI base units:
| extradata = 1 t = 1000 kg = 1 Mg
}}{{About|the metric unit of mass|other ton units|Ton|other uses of tonne|Tonne (disambiguation)|other uses of "megagram"|Megagram (geometry)}}

The tonne ({{IPAc-en|audio=En-us-tonne.ogg|t|ʌ|n}}; non-SI unit, symbol: t), commonly referred to as the metric ton in the United States and Canada, is a non-SI metric unit of mass equal to 1,000 kilograms[1][2][3][4] or one megagram (symbol: Mg). It is equivalent to approximately {{nowrap|2,204.6}} pounds,[5] {{nowrap|1.102 short tons (US)}} or 0.984 long tons (UK). Although not part of the SI, the tonne is accepted for use with SI units and prefixes by the International Committee for Weights and Measures.[6]

The tonne is derived from the weight of 1 cubic metre of pure water; 1,000 litres of pure water weighs about one tonne.

Symbol and abbreviations

The SI symbol for the tonne is 't', adopted at the same time as the unit in 1879.[2] Its use is also official for the metric ton in the United States, having been adopted by the United States National Institute of Standards and Technology.[8] It is a symbol, not an abbreviation, and should not be followed by a period. Use of upper and lower case is significant, and use of other letter combinations is not permitted and would lead to ambiguity. For example, 'T', 'MT', 'Mt', 'mt' are the SI symbols for the tesla, megatesla, megatonne (one teragram) and millitonne (one kilogram) respectively. If describing TNT equivalent units of energy, this is equivalent to 4.184 petajoules.

Origin and spelling

In French and all English-speaking countries that are predominantly metric, tonne is the correct spelling. It is usually pronounced the same as ton {{IPAc-en|t|ʌ|n}}, but when it is important to clarify that the metric term is meant, rather than short ton, the final "e" can also be pronounced, i.e. "tonny" {{IPAc-en|ˈ|t|ʌ|n|ɪ}}.[7] In Australia, it is also pronounced {{IPAc-en|t|ɒ|n}}.[8]

Before metrication in the UK the unit used for most purposes was the Imperial ton of 2,240 pounds avoirdupois or 20 hundredweight (usually referred to as the long ton in the US), equivalent to 1,016 kg, differing by just 1.6% from the tonne. The UK Weights and Measures Act 1985 explicitly excluded from use for trade certain imperial units, including the ton, unless the item being sold or the weighing equipment being used was weighed or certified prior to 1 December 1980, and even then only if the buyer was made aware that the weight of the item was measured in imperial units.[9]{{Full citation needed|date=October 2015}}[10][11]

In the United States metric ton is the name for this unit used and recommended by NIST;[12] an unqualified mention of a ton almost invariably refers to a short ton of {{convert|2000|lb|kg|sigfig=3}}, and tonne is rarely used in speech or writing.

Ton and tonne are both derived from a Germanic word in general use in the North Sea area since the Middle Ages (cf. Old English and Old Frisian tunne, Old High German and Medieval Latin tunna, German and French tonne) to designate a large cask, or tun.[13] A full tun, standing about a metre high, could easily weigh a tonne. An English tun (an old wine cask volume measurement equivalent to 954 litres) of wine weighs roughly a tonne, 954 kg if full of water, a little less for wine.

The spelling tonne pre-dates the introduction of the SI in 1960; it has been used with this meaning in France since 1842,[14] when there were no metric prefixes for multiples of 106 and above, and is now used as the standard spelling for the metric mass measurement in most English-speaking countries.[15][16][17][18] In the United States, the unit was originally referred to using the French words millier or tonneau,[19] but these terms are now obsolete.[3] The Imperial and US customary units comparable to the tonne are both spelled ton in English, though they differ in mass.

Conversions

One tonne is equivalent to:

  • Metric/SI: 1 megagram (Mg) (by definition). Equal to {{val|1000000|u=grams (g)}} or {{val|1000|u=kilograms (kg)}}.
    • Megagram, Mg, is the official SI unit. Mg is distinct from mg, milligram.
  • Pounds (lb): Exactly {{sfrac|1000|0.453 592 37}} lb (by definition of the pound),[20] or approximately {{val|2204.622622|u=lb}} (10 {{abbr|s.f.|significant figures}}).
  • US/Short tons (ST): Exactly {{sfrac|1|0.907 184 74}} short tons, or approximately {{val|1.102311311}} ST (10 {{abbr|s.f.|significant figures}}).
    • One short ton is exactly {{val|0.90718474|u=t}}.[21]
  • Imperial/Long tons (LT): Exactly {{sfrac|1|1.016 046 9088}} long tons, or approximately {{val|0.9842065276}} LT (10 {{abbr|s.f.|significant figures}}).
    • One long ton is exactly {{val|1.0160469088|u=t}}.[21]

Derived units

For multiples of the tonne, it is more usual to speak of thousands or millions of tonnes. Kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events in equivalent mass of TNT, often loosely as approximate figures. When used in this context, there is little need to distinguish between metric and other tons, and the unit is spelt either as ton or tonne with the relevant prefix attached.[22]

TonnesGramsEquivalents*
Multiple Name Symbol Multiple Name Symbol Tonnes (t) Kilograms (kg) Grams (g) US/short tons (ST)† Imperial/long tons (LT)†
100 tonne t106 megagram Mg1 t 1,000 kg 1 million g 1|t|ST|disp=output number only|sigfig=5}} ST1|t|LT|disp=output number only|sigfig=5}} LT
103 kilotonne ktǂ109 gigagram Gg 1,000 t 1 million kg 1 billion g 1000|t|ST|disp=output number only|sigfig=5}} ST1000|t|LT|disp=output number only|sigfig=5}} LT
106 megatonne Mt1012 teragram Tg 1 million t 1 billion kg 1 trillion g1|t|ST|disp=output number only|sigfig=5}} million ST1000000|t|LT|disp=output number only|sigfig=5}} LT
109 gigatonneGt1015 petagramPg 1 billion t 1 trillion kg 1 quadrillion g1|t|ST|disp=output number only|sigfig=5}} billion ST1000|t|LT|disp=output number only|sigfig=5}} million LT
1012 teratonneTt1018 exagramEg}} 1 trillion t 1 quadrillion kg 1 quintillion g 1|t|ST|disp=output number only|sigfig=5}} trillion ST1000|t|LT|disp=output number only|sigfig=5}} billion LT
1015 petatonnePt1021 zettagramZg 1 quadrillion t 1 quintillion kg 1 sextillion g1|t|ST|disp=output number only|sigfig=5}} quadrillion ST1000|t|LT|disp=output number only|sigfig=5}} trillion LT
1018 exatonneEt1024 yottagramYg 1 quintillion t 1 sextillion kg 1 septillion g1|t|ST|disp=output number only|sigfig=5}} quintillion ST1000|t|LT|disp=output number only|sigfig=5}} quadrillion LT
*The equivalent units columns use the short scale large-number naming system currently used in most English-language countries, e.g. 1 billion = 1,000 million = 1,000,000,000.
†Values in the equivalent short and long tons columns are rounded to five significant figures, see Conversions for exact values.
ǂThough non-standard, the symbol "kt" is also used for knot, a unit of speed for aircraft and sea-going vessels, and should not be confused with kilotonne.

Alternative usage

A metric ton unit (mtu) can mean {{convert|10|kg|lbs|sigfig=2}} within metal (e.g. tungsten, manganese) trading, particularly within the US. It traditionally referred to a metric ton of ore containing 1% (i.e. 10 kg) of metal.[23][24]

The following excerpt from a mining geology textbook describes its usage in the particular case of tungsten:

"Tungsten concentrates are usually traded in metric tonne units (originally designating one tonne of ore containing 1% of WO3, today used to measure WO3 quantities in 10 kg units. One metric tonne unit (mtu) of tungsten (VI) contains 7.93 kilograms of tungsten." (Walter L Pohl, Economic Geology: Principles and Practices, English edition, 2011, p 183.)

Note that tungsten is also known as wolfram and has the atomic symbol W.

In the case of uranium, the acronym MTU is sometimes considered to be metric ton of uranium, meaning 1,000 kg.[25][26][27][28]

A gigatonne of carbon dioxide equivalent (GtCO2eq) is a unit used by the UN climate change panel, IPCC, to measure the effect of a technology or process on global warming.

===Use of mass as proxy for energy===

{{Main article|TNT equivalent}}

The tonne of trinitrotoluene (TNT) is used as a proxy for energy, usually of explosions (TNT is a common high explosive). Prefixes are used: kiloton(ne), megaton(ne), gigaton(ne), especially for expressing nuclear weapon yield, based on a specific combustion energy of TNT of about 4.2 MJ/kg (or one thermochemical calorie per milligram). Hence, 1 t TNT = 4.2 GJ, 1 kt TNT = 4.2 TJ, 1 Mt TNT = 4.2 PJ.

The SI unit of energy is the joule. Assuming that a TNT explosion releases 1,000 small (thermochemical) calories per gram (4.2 kJ/g), one tonne of TNT is equivalent to 4.2 gigajoules.

In the petroleum industry the tonne of oil equivalent (toe) is a unit of energy: the amount of energy released by burning one tonne of crude oil, approximately 42 GJ. There are several slightly different definitions. This is ten times as much as a tonne of TNT because atmospheric oxygen is used.

Unit of force

Like the gram and the kilogram, the tonne gave rise to a (now obsolete) force unit of the same name, the tonne-force, equivalent to about 9.8 kilonewtons: a unit also often called simply "tonne" or "metric ton" without identifying it as a unit of force. In contrast to the tonne as a mass unit, the tonne-force or metric ton-force is not acceptable for use with SI, partly because it is not an exact multiple of the SI unit of force, the newton.

See also

  • Ton
    • Short ton
    • Long ton
    • Tonnage
    • Ton (volume)
  • Metre–tonne–second system of units
  • Tonne of oil equivalent
  • Orders of magnitude (mass)

Notes and references

1. ^Weights and Measures Act 1985. National Archives (London), 2014. Accessed 13 Aug 2014.
2. ^1 Table 6 {{webarchive|url=https://web.archive.org/web/20091001100650/http://www.bipm.org/en/si/si_brochure/chapter4/table6.html |date=2009-10-01 }}. BIPM. Retrieved on 2011-07-10.
3. ^1 {{cite journal|title=Metric System of Measurement: Interpretation of the International System of Units for the United States|journal=Federal Register|date=July 28, 1998|volume=63|issue=144|id=63 FR 40333|page=40338|url=http://physics.nist.gov/cuu/pdf/SIFedReg.pdf|format=PDF|deadurl=yes|archiveurl=https://web.archive.org/web/20111015081850/http://physics.nist.gov/cuu/pdf/SIFedReg.pdf|archivedate=October 15, 2011|df=}}
4. ^The International System of Units (SI) (PDF), 8th Edition, 2006, Section 4.1
5. ^{{cite web|url=http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf|author=United States National Bureau of Standards|title=Notices "Refinement of values for the yard and the pound"|date=1959-06-25|accessdate=2006-08-12}}
6. ^{{cite web|url=https://www.nist.gov/pml/pubs/sp811/appenb8.cfm#T|title=NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically|first=Pamela L|last=Corey|date=1 February 2016|publisher=}}
7. ^The Oxford English dictionary 2nd ed. lists both /tʌn/ and /ˈtʌnɪ/
8. ^{{cite book |authorlink= |title= Macquarie Dictionary|edition= fifth |url= |accessdate= |year= 2009|publisher= Macquarie Dictionary Publishers Pty Ltd|location= Sydney|isbn= |page= |pages=}}
9. ^A Dictionary of Weights, Measures, and Units, edited by Donald Fenna, Oxford University Press
10. ^{{cite act| title = Weights and Measures Act 1985| type = Act| number = 72| language = English| date = 30 October 1985| article = 8(1)| article-type= Section| url = http://www.legislation.gov.uk/ukpga/1985/72| access-date = 11 Apr 2016}}
11. ^{{cite act| title = Weights and Measures Act 1985| type = Act| number = 72| language = English| date = 30 October 1985| article = 11(13 - 14)| article-type= Schedule| url = http://www.legislation.gov.uk/ukpga/1985/72| access-date = 11 Apr 2016}}
12. ^1 Metric System of Measurement: Interpretation of the International System of Units for the United States (PDF). See corrections in the Errata section of  .
13. ^{{OEtymD|tonne}}
14. ^{{cite web|url=http://atilf.atilf.fr/dendien/scripts/tlfiv4/showps.exe?p=combi.htm;java=no;|title=Recherche d'un mot|website=atilf.atilf.fr}}
15. ^{{cite web|url=http://www.nmo.bis.gov.uk/Docs/Legislation/Units%20of%20Measurement/Gnotes%20for%20public%20sector%20on%20use%20of%20metric.pdf|title=Guidance Note on the use of Metric Units of Measurement by the Public Sector|year=2007|publisher=National Measurement Office|accessdate=2010-02-13|deadurl=yes|archiveurl=http://webarchive.nationalarchives.gov.uk/20110207120946/http://www.nmo.bis.gov.uk/Docs/Legislation/Units%20of%20Measurement/Gnotes%20for%20public%20sector%20on%20use%20of%20metric.pdf|archivedate=2011-02-07|df=}} "Tonne" is listed under "The Principal Metric Units of Measurement" on p. 7.
16. ^{{cite web|url= http://www.comlaw.gov.au/ComLaw/Legislation/LegislativeInstrumentCompilation1.nsf/framelodgmentattachments/35F21696B4C9E27CCA2575EC001FA5D1|title= National Measurement Regulations 1999 ||year=1999|publisher=Australian Government|accessdate=2010-02-13}} "Tonne" is listed under Schedule 1, Part 3 as a non-SI unit of measurement used with SI units of measurement.
17. ^{{cite web |url= http://www.maf.govt.nz/statistics/forestry/annual/nzstats2000/appendix/append4.htm|title= Appendix 4: Units of Measurement and Conversion Factors|work= |publisher= MAF (Ministry of Agriculture and Forestry (New Zealand))|accessdate=2010-02-13}}
18. ^{{cite web|url= http://www.gazette.gc.ca/archives/p2/1999/1999-11-10/html/sor-dors430-eng.html|title=Canada Gazette|date= 1998–2007|publisher=Government of Canada|accessdate=2010-02-13|quote=The Corporation shall pay to producers selling and delivering wheat produced in the designated area to the Corporation the following sums certain per tonne basis...}}
19. ^Act of July 28, 1866, codified in {{UnitedStatesCode|15|205}}
20. ^{{Cite book | title=Weights and measures standards of the United States – A brief history | year=1976 | url=http://physics.nist.gov/Pubs/SP447/contents.html | first=L.E. | last=Barbrow | author2=Judson, L.V. | deadurl=yes | archiveurl=https://web.archive.org/web/20080511153143/http://physics.nist.gov/Pubs/SP447/contents.html | archivedate=2008-05-11 | df= }}
21. ^1 National Institute of Standards and Technology. {{cite book |date=October 2013 |chapter=Appendix C – General Tables of Units of Measurement |chapterurl=https://www.nist.gov/pml/wmd/pubs/upload/appc-14-hb44-final.pdf |editor1-last=Butcher |editor1-first=Tina |editor2-last=Crown |editor2-first=Linda |editor3-last=Harshman |editor3-first=Rick |editor4-last=Williams |editor4-first=Juana |title=Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices |url=https://www.nist.gov/pml/wmd/pubs/hb44-14.cfm |series=NIST Handbook |volume=44 |edition=2014 |location=Washington, D.C. |publisher=U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology |page=C-13 |issn=0271-4027 |oclc=58927093 |accessdate=10 December 2013}}
22. ^The Oxford English Dictionary 2nd ed. gives both megaton and megatonne and adds "The unit may be calculated in either imperial or metric tons; the form megatonne generally implies the metric unit". The use for energy is the first definition; use for mass or weight is the third definition.
23. ^{{cite web|url=http://www.emis.platts.com/thezone/guides/platts/metals/conversion.html|title=Platt's Metals Guide to Specifications - Conversion Tables|date=8 September 2008|publisher=|deadurl=bot: unknown|archiveurl=https://web.archive.org/web/20080908055702/http://www.emis.platts.com/thezone/guides/platts/metals/conversion.html|archivedate=8 September 2008|df=}}
24. ^How Many? A Dictionary of Units of Measurement. Unc.edu. Retrieved on 2011-07-10.
25. ^Reference.Pdf. (PDF) . Retrieved on 2011-07-10.
26. ^"Glossary". (June 2000). Disposition of Surplus Hanford Site Uranium, Hanford Site, Richland, Washington. US Department of Energy.
27. ^"Acronyms". Y-12 National Security Complex.
28. ^[https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0544/r4/ NRC Collection of Abbreviations (NUREG-0544, Rev. 4), United States Nuclear Regulatory Commission]. Nrc.gov (2011-03-13). Retrieved on 2011-07-10.

External links

  • NIST Special Publication 811, Guide for the Use of the International System of Units (SI)
{{SI units}}

2 : Non-SI metric units|Units of mass
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