Newton (unit) explained (2024)

The newton (symbol: N) is the unit of force in the International System of Units (SI). It is defined as

1 kg ⋅ m/s²

, the force which gives a mass of 1kilogram an acceleration of 1metre per second squared.

It is named after Isaac Newton in recognition of his work on classical mechanics, specifically his second law of motion.

Definition

A newton is defined as

1 kg{ ⋅ m/s^2}

(it is a named derived unit defined in terms of the SI base units).^[1] One newton is, therefore, the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force.^[2]

The units "metre per second squared" can be understood as measuring a rate of change in velocity per unit of time, i.e. an increase in velocity by 1metre per second every second.

In 1946, the General Conference on Weights and Measures (CGPM) Resolution2 standardized the unit of force in the MKS system of units to be the amount needed to accelerate 1kilogram of mass at the rate of 1metre per second squared. In 1948, the 9th CGPM Resolution7 adopted the name newton for this force.^[3] The MKS system then became the blueprint for today's SI system of units.^[4] The newton thus became the standard unit of force in the French: Système international d'unités (SI), or International System of Units.

The connection to Newton comes from Newton's second law of motion, which states that the force exerted on an object is directly proportional to the acceleration hence acquired by that object, thus:^[5] $$F\; =\; ma,$$where

m

represents the mass of the object undergoing an acceleration

a

. When using the SI unit of mass, the kilogram (

kg

), and SI units for distance metre (

m

), and time, second (

s

) we arrive at the SI definition of the newton:$\backslash mathrm.$

Examples

At average gravity on Earth (conventionally,

g={9.80665} m/s²

), a kilogram mass exerts a force of about 9.8newtons.

• An average-sized apple at 200 exerts about two newtons of force at Earth's surface, which we measure as the apple's weight on Earth.

0.200kg x 9.80665m/s²=1.961N.

• An average adult exerts a force of about 608N on Earth.

62kg x 9.80665m/s^2=608N

(where 62kg is the world average adult mass).^[6]

Kilonewtons

Large forces may be expressed in kilonewtons (kN), where . For example, the tractive effort of a Class Y steam train locomotive and the thrust of an F100 jet engine are both around 130kN.

Climbing ropes are tested by assuming a human can withstand a fall that creates 12kN of force. The ropes must not break when tested against 5 such falls.^[7]

Conversion factors

See also

• 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, 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

Notes and References

1. Book: Bureau International des Poids et Mesures . The International System of Units (SI) . Bureau International des Poids et Mesures (BIPM) . 2019 . 9 . 137 . PDF . 22 September 2021 . 30 September 2021 . https://web.archive.org/web/20210930221014/https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507?version=1.10&download=true . live .
2. Web site: 17 December 2020 . Newton unit of measurement . live . https://web.archive.org/web/20190927032140/https://www.britannica.com/science/newton-unit-of-measurement . 27 September 2019 . 27 September 2019 . Encyclopædia Britannica.
3. Book: The International System of Units (SI) . . 1977 . 9282220451 . 1977 . 17. 15 November 2015 . 11 May 2016 . https://web.archive.org/web/20160511160701/https://books.google.com/books?id=YvZNdSdeCnEC&pg=PA17.
4. Book: David B. Newell . Eite Tiesinga . The International System of Units (SI) . 30 November 2019 . . Gaithersburg, MD . 2019. NIST Special publication 330, 2019.
5. Web site: Table 3. Coherent derived units in the SI with special names and symbols . The International System of Units (SI) . . 2006 . dead . https://web.archive.org/web/20070618123613/http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html . 18 June 2007 .
6. Walpole . Sarah Catherine . Prieto-Merino . David . Edwards . Phillip . Cleland . John . Stevens . Gretchen . Roberts . Ian . 2 . 18 June 2012 . The weight of nations: an estimation of adult human biomass . . 12 . 12 . 439 . 10.1186/1471-2458-12-439 . 3408371 . 22709383 . free .
7. Bright, Casandra Marie. "A History of Rock Climbing Gear Technology and Standards." (2014).