View source for Newton (unit)

{{distinguish|text=[[Newton scale]], a rarely used non-SI temperature scale}}
{{short description|Unit of force in physics}}
{{redirects|Newtons|the snack|Newtons (cookie)}}
{{Use British English Oxford spelling|date=May 2018}}
{{Infobox unit
| bgcolour =
| name = newton
| image = One Newton, illustrated (transparent background).svg
| caption = Visualization of one newton of force
| standard = [[SI derived unit]]
| quantity = [[Force]]
| symbol = N
| namedafter = [[Sir Isaac Newton]]
| units1 = SI base units
| inunits1     = 1 [[kilogram|kg]]⋅[[metre|m]]⋅[[second|s]]<sup>−2</sup>
| units2       = Imperial units
| inunits2     = {{convert|1|N|sigfig=7|disp=out}}
}}
The '''newton'''  (symbol: '''N''') is defined as the force which gives a mass of 1 kilogram an acceleration of 1 metre per second. It is the [[International System of Units]] (SI) [[SI derived unit|derived unit]] of [[force]]. It is named after [[Isaac Newton]] in recognition of his work on [[classical mechanics]], specifically [[Newton's laws of motion#Newton's second law|Newton's second law of motion]]. 
When converted into dynes(CGS), 1N = 10 DYNES.

==Definition==
A newton is defined as 1 kg⋅m/s{{sup|2}} (it is a derived unit which is defined in terms of the [[SI base unit]]s).<ref>{{cite book |title=The International System of Units – 9th edition – Text in English |date=2019 |publisher=Bureau International des Poids et Mesures (BIPM) |page=137 |edition=9 |url=https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507?version=1.10&download=true}}</ref> One newton is therefore the force needed to [[Acceleration|accelerate]] one [[kilogram]] of mass at the rate of one [[metre per second squared]] in the direction of the applied force.<ref>{{Cite web|url=https://www.britannica.com/science/newton-unit-of-measurement|title=Newton {{!}} unit of measurement|website=Encyclopedia Britannica|language=en|access-date=2019-09-27|archive-date=2019-09-27|archive-url=https://web.archive.org/web/20190927032140/https://www.britannica.com/science/newton-unit-of-measurement|url-status=live}}</ref>
The units "metre per second squared" can be understood as a change in [[velocity]] per time, i.e. an increase of velocity by 1 metre per second every second.

In 1946, [[Conférence Générale des Poids et Mesures]] (CGPM) Resolution 2 standardized the unit of force in the [[MKS system of units]] to be the amount needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared. In 1948, the 9th CGPM Resolution 7 adopted the name ''newton'' for this force.<ref name="ISU1977">{{Citation | author = International Bureau of Weights and Measures | title = The International System of Units | issue = 330–331 | edition = 3rd | publisher = U.S. Dept. of Commerce, National Bureau of Standards | page = 17 | year = 1977 | isbn = 0745649742 | url = https://books.google.com/books?id=YvZNdSdeCnEC&pg=PA17 | postscript = . | access-date = 2015-11-15 | archive-date = 2016-05-11 | archive-url = https://web.archive.org/web/20160511160701/https://books.google.com/books?id=YvZNdSdeCnEC&pg=PA17 | url-status = live }}</ref> The MKS system then became the blueprint for today's SI system of units. The newton thus became the standard unit of force in the {{lang|fr|Système international d'unités}} (SI), or [[International System of Units]].

{{SI unit lowercase|Isaac Newton|newton|N}}

In more formal terms, [[Newton's laws of motion|Newton's second law of motion]] states that the force exerted on an object is directly proportional to the acceleration hence acquired by that object, namely:<ref>{{cite web | title = Table 3. Coherent derived units in the SI with special names and symbols | work = The International System of Units (SI) | publisher = [[International Bureau of Weights and Measures]] | year = 2006 | url = http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html | url-status = dead | archive-url = https://web.archive.org/web/20070618123613/http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html | archive-date = 2007-06-18 }}</ref>
: <math>F = ma,</math>
where <math>m</math> represents the [[mass]] of the object undergoing an acceleration <math>a</math>. As a result, the ''newton'' may be defined in terms of kilograms (<math>\text{kg}</math>), [[metre]]s (<math>\text{m}</math>), and [[second]]s (<math>\text{s}</math>) as
: <math>1\ \text{N} = 1\ \frac{\text{kg} \cdot \text{m}}{\text{s}^2}.</math>

==Examples==

At average [[Gravity of Earth|gravity on Earth]] (conventionally, {{val|9.80665|ul=m/s2|p={{math|''g''}} =&nbsp;}}), a kilogram mass exerts a force of about 9.8&nbsp;newtons. An average-sized apple exerts about one newton of force, which we measure as the apple's weight.<ref>{{cite web |url=https://www.myfooddata.com/articles/how-much-is-100-grams.php |last=Whitbread BSc (Hons) MSc DipION |first=Daisy |title=How much is 100 grams? |access-date=22 September 2020 |archive-date=24 October 2017 |archive-url=https://web.archive.org/web/20171024043017/https://www.healthaliciousness.com/blog/How-much-is-100-grams.php |url-status=live }}</ref>
: 1 N = 0.10197 kg × 9.80665 m/s<sup>2</sup>{{spaces|3}} ({{val|0.10197|ul=kg|s= &nbsp;= 101.97 g}}).

The weight of an [[Human body weight#Average weight around the world|average adult]] exerts a force of about 608&nbsp;N.
: 608&nbsp;N = 62&nbsp;kg × 9.80665 m/s<sup>2</sup> (where 62&nbsp;kg is the world average adult mass).<ref>{{cite journal | title = The weight of nations: an estimation of adult human biomass | last1 = Walpole | first1 = Sarah Catherine | first2 = David | last2 = Prieto-Merino | first3 = Phillip | last3 = Edwards | first4 = John | last4 = Cleland | first5 = Gretchen  | last5 = Stevens | first6 = Ian | last6 = Roberts | journal = BMC Public Health |volume = 12| issue = 12 | page = 439 | year = 2012 | doi = 10.1186/1471-2458-12-439|pmid = 22709383| pmc = 3408371 }}</ref>

==Kilonewtons==
[[File:Dwire carabiner.jpg|thumb|right|A [[carabiner]] used in [[rock climbing]], with a safety rating of 26&nbsp;kN when loaded along the spine with the gate closed, 8&nbsp;kN when loaded perpendicular to the spine, and 10&nbsp;kN when loaded along the spine with the gate open.]]
It is common to see forces expressed in kilonewtons (kN), where {{nowrap|1 kN {{=}} 1000 N}}. For example, the [[tractive effort]] of [[NER Class Y|a Class Y steam train locomotive]] and the [[thrust]] of an [[Pratt & Whitney F100|F100 jet engine]] are both around 130&nbsp;kN.

One kilonewton, 1&nbsp;kN, is equivalent to {{convert|1|kN|kgf|1|disp=out|lk=on}}, or about 100&nbsp;kg of load under Earth gravity.

: 1 kN = 102 kg &times; 9.81 m/s<sup>2</sup>.

So for example, a platform that shows it is rated at {{convert|321|kN}} will safely support a {{convert|32100|kg|adj=on}} load.

Specifications in kilonewtons are common in safety specifications for:
* the holding values of [[fasteners]], [[Earth anchor]]s, and other items used in the [[Construction|building]] industry;
* working loads in [[Tension (physics)|tension]] and in [[Shear stress|shear]];
* [[rock-climbing equipment]];
* [[thrust]] of [[rocket engine]]s, [[Jet engine]]s and [[launch vehicle]]s;
* clamping forces of the various moulds in injection-moulding machines used to manufacture plastic parts.

==Conversion factors==
{{Units of force}}
{{GravEngAbs}}
{{SI prefixes (inline table)|floatleft}}
{{clear}}

==See also==
{{div col|colwidth=30em}}
* [[Force gauge]]
* [[International System of Units]] (SI)
* [[Joule]], SI unit of [[energy]], 1 newton exerted over a distance of 1 metre
* [[Kilogram-force]], force exerted by Earth's gravity at sea level on one kilogram of mass
* [[Kip (unit)]]
* [[Pascal (unit)|Pascal]], SI unit of [[pressure]], 1 newton acting on an area of 1 [[square metre]]
* [[Orders of magnitude (force)]]
* [[Pound (force)]]
* [[Sthène]]
* [[Newton metre]], SI unit of [[torque]]
{{div col end}}

== References ==
{{Reflist}}

{{SI units}}
{{Isaac Newton}}

[[Category:Units of force]]
[[Category:SI derived units]]
[[Category:Isaac Newton]]