The newton (symbol: N) is the International System of Units (SI) derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion.
See below for the conversion factors.
One newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in direction of the applied force.
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.^{[1]} 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 Système international d'unités (SI), or International System of Units.
This SI unit is named after Isaac Newton. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is upper case (N). However, when an SI unit is spelled out in English, it should always begin with a lower case letter (newton)—except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.— Based on The International System of Units, section 5.2.
Newton's second law of motion states that F = ma, where F is the force applied, m is the mass of the object receiving the force, and a is the acceleration of the object. The newton is therefore:^{[2]}
F | = | m | ⋅ | a |
1 N | = | 1 kg | ⋅ | 1 m/s^{2} |
where the following symbols are used for the units: N for newton, kg for kilogram, m for metre, and s for second.
where is force, is mass, is length and is time.
At average gravity on Earth (conventionally, g = 9.80665 m/s^{2}), a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force, which we measure as the apple's weight.^{[3]}
The weight of an average adult exerts a force of about 550 – 800 N.
It is common to see forces 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 fighter jet engine are both around 130 kN.
One kilonewton, 1 kN, is 102.0 kgf, or about 100 kg of load.
So for example, a platform that shows it is rated at 321 kilonewtons (72,000 lb_{f}), will safely support a 32,100 kilograms (70,800 lb) load.
Specifications in kilonewtons are common in safety specifications for:
newton (SI unit) |
dyne | kilogram-force, kilopond |
pound-force | poundal | |
---|---|---|---|---|---|
1 N | ≡ 1 kg⋅m/s^{2} | = 10^{5} dyn | ≈ 0.10197 kp | ≈ 0.22481 lbf | ≈ 7.2330 pdl |
1 dyn | = 10^{−5} N | ≡ 1 g⋅cm/s^{2} | ≈ 1.0197 × 10^{−6} kp | ≈ 2.2481 × 10^{−6} lbf | ≈ 7.2330 × 10^{−5} pdl |
1 kp | = 9.80665 N | = 980665 dyn | ≡ g_{n} ⋅ (1 kg) | ≈ 2.2046 lbf | ≈ 70.932 pdl |
1 lbf | ≈ 4.448222 N | ≈ 444822 dyn | ≈ 0.45359 kp | ≡ g_{n} ⋅ (1 lb) | ≈ 32.174 pdl |
1 pdl | ≈ 0.138255 N | ≈ 13825 dyn | ≈ 0.014098 kp | ≈ 0.031081 lbf | ≡ 1 lb⋅ft/s^{2} |
The value of g_{n} as used in the official definition of the kilogram-force is used here for all gravitational units. |
Base | Force | Weight | Mass | |||||
---|---|---|---|---|---|---|---|---|
2nd law of motion | m = F/a | F = W ⋅ a/g | F = m ⋅ a | |||||
System | BG | GM | EE | M | AE | CGS | MTS | SI |
Acceleration (a) | ft/s^{2} | m/s^{2} | ft/s^{2} | m/s^{2} | ft/s^{2} | gal | m/s^{2} | m/s^{2} |
Mass (m) | slug | hyl | pound-mass | kilogram | pound | gram | tonne | kilogram |
Force (F), weight (W) |
pound | kilopond | pound-force | kilopond | poundal | dyne | sthène | newton |
Pressure (p) | pound per square inch | technical atmosphere | pound-force per square inch | atmosphere | poundal per square foot | barye | pieze | pascal |
Multiples | Prefix name | deca | hecto | kilo | mega | giga | tera | peta | exa | zetta | yotta | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Prefix symbol | da | h | k | M | G | T | P | E | Z | Y | ||
Factor | 10^{0} | 10^{1} | 10^{2} | 10^{3} | 10^{6} | 10^{9} | 10^{12} | 10^{15} | 10^{18} | 10^{21} | 10^{24} | |
Submultiples | Prefix name | deci | centi | milli | micro | nano | pico | femto | atto | zepto | yocto | |
Prefix symbol | d | c | m | μ | n | p | f | a | z | y | ||
Factor | 10^{0} | 10^{−1} | 10^{−2} | 10^{−3} | 10^{−6} | 10^{−9} | 10^{−12} | 10^{−15} | 10^{−18} | 10^{−21} | 10^{−24} |