Newton (unit)

The newton (symbol: N) is the unit of force in the International System of Units (SI). Expressed in terms of SI base units, it is 1 kg⋅m/s², the force that accelerates a mass of one kilogram at one metre per second squared.

The unit 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/s² (it is a named derived unit defined in terms of the SI base units).Template:Rp 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.

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 one metre per second every second.

In 1946, the General Conference on Weights and Measures (CGPM) Resolution 2 standardized the unit of force in the MKS system of units to be the amount needed to accelerate one kilogram of mass at the rate of one metre per second squared. In 1948, the 9th CGPM Resolution 7 adopted the name newton for this force. 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 (SI), or International System of Units.

The newton is named after Isaac Newton. As with every SI unit named after a person, its symbol starts with an upper case letter (N), but when written in full, it follows the rules for capitalisation of a common noun; i.e., newton becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.

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: $$F=ma,$$ 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: 1 kg⋅m/s².

Examples

At average gravity on Earth (conventionally, $g_{\text{n}}$ = Template:Val), a kilogram mass exerts a force of about 9.81 N.

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

$0.200\text{ kg}\times 9.80665{\text{ m/s}}^2=1.961\text{ N}.$

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

$62\text{ kg}\times 9.80665{\text{ m/s}}^2=608\text{ N}$ (where 62 kg is the world average adult mass).

Kilonewtons

File:Dwire carabiner.jpg

A carabiner used in rock climbing, with a safety rating of 26 kN when loaded along the spine with the gate closed, 8 kN when loaded perpendicular to the spine, and 10 kN when loaded along the spine with the gate open.

Large forces may be expressed in kilonewtons (kN), where 1 kN = 1000 N. For example, the tractive effort of a Class Y steam train locomotive and the thrust of an F100 jet engine are both around 130 kN.

Climbing ropes are tested by assuming a human can withstand a fall that creates 12 kN of force. The ropes must not break when tested against 5 such falls.Template:Rp

Conversion factors

Units of force

	newton	dyne	kilogram-force, REDIRECT Template:Breakkilopond	pound-force	poundal
1Template:NbspN	≡Template:NbspTemplate:Val	=Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val
1Template:Nbspdyn	=Template:NbspTemplate:Val	≡Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val
1Template:Nbspkp	=Template:NbspTemplate:Val	=Template:NbspTemplate:Val	≡Template:NbspgnTemplate:Nbsp×Template:Nbsp1Template:Nbspkg	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val
Template:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≡Template:NbspgnTemplate:Nbsp×Template:NbspTemplate:Val	≈Template:NbspTemplate:Val
1Template:Nbsppdl	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≈Template:NbspTemplate:Val	≡Template:NbspTemplate:Val
The value of gn (Template:Val) as used in the official definition of the kilogram-force is used here for all gravitational units.

SI multiples of newton (N)

Submultiples			Multiples
Value	SI symbol	Name	Value	SI symbol	Name
10−1 N	dN	decinewton	101 N	daN	decanewton
10−2 N	cN	centinewton	102 N	hN	hectonewton
10−3 N	mN	millinewton	103 N	kN	kilonewton
10−6 N	μN	micronewton	106 N	MN	meganewton
10−9 N	nN	nanonewton	109 N	GN	giganewton
10−12 N	pN	piconewton	1012 N	TN	teranewton
10−15 N	fN	femtonewton	1015 N	PN	petanewton
10−18 N	aN	attonewton	1018 N	EN	exanewton
10−21 N	zN	zeptonewton	1021 N	ZN	zettanewton
10−24 N	yN	yoctonewton	1024 N	YN	yottanewton
10−27 N	rN	rontonewton	1027 N	RN	ronnanewton
10−30 N	qN	quectonewton	1030 N	QN	quettanewton

See also

• Force gauge
• International System of Units (SI)
• Joule, SI unit of energy, 1 newton exerted over a displacement 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