Newton (unit)

Not to be confused with Newton scale, a rarely used non-SI temperature scale.
Newton
Unit system: SI derived unit
Unit of... Force
Symbol: N
Named after: Isaac Newton
In SI base units: 1 N = 1 kg·m/s2

The newton (symbol: N) is the 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.

Contents

Definition

The newton is the SI unit for force; it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one metre per second squared. Newton's second law of motion states: F = ma, multiplying m (kg) by a (m/s2), The newton is therefore:[1]

{\rm N = kg~\frac{m}{s^2}}

Units used:

N = newton
kg = kilogram
m = metre
s = second

In dimensional analysis:

Force = \frac{\bold M \bold L} {{\bold T^2}}

where

M = Mass
L = Length
T = Time

Examples

Common use of kilonewtons in construction

Kilonewtons are often used for stating safety holding values of fasteners, anchors, and more in the building industry. They are also often used in the specifications for rock climbing equipment. The safe working loads in both tension and shear measurements can be stated in kilonewtons. Injection moulding machines, used to manufacture plastic parts, are classed by kilonewton (i.e., the amount of clamping force they apply to the mould).

On the Earth's surface, 1 kN is about 101.97162 kilogram-force of load, but multiplying the kilonewton value by 100 (i.e. using a slightly conservative and easier to calculate value) is a good rule of thumb.[2]

Conversion factors

Units of force
newton
(SI unit)		 dyne kilogram-force,
kilopond		 pound-force poundal
1 N ≡ 1 kg·m/s² = 105 dyn ≈ 0.10197 kp ≈ 0.22481 lbF ≈ 7.2330 pdl
1 dyn = 10−5 N ≡ 1 g·cm/s² ≈ 1.0197×10−6 kp ≈ 2.2481×10−6 lbF ≈ 7.2330×10−5 pdl
1 kp = 9.80665 N = 980665 dyn ≡ gn·(1 kg) ≈ 2.2046 lbF ≈ 70.932 pdl
1 lbF ≈ 4.448222 N ≈ 444822 dyn ≈ 0.45359 kp ≡ gn·(1 lb) ≈ 32.174 pdl
1 pdl ≈ 0.138255 N ≈ 13825 dyn ≈ 0.014098 kp ≈ 0.031081 lbF ≡ 1 lb·ft/s²
The value of gn as used in the official definition of the kilogram-force is used here for all gravitational units.
Three approaches to mass and force units[3] [4]
Base force, length, time weight, length, time mass, length, time
Force (F) F = m\cdot {a} = w\cdot\tfrac{a}{g} F = m\cdot\tfrac{a}{g_c} = w\cdot\tfrac{a}{g} F = m\cdot {a} = w\cdot\tfrac{a}{g}
Weight (w) w = m\cdot g w = m\cdot\tfrac{g}{g_c} \approx m w = m\cdot g
System BG GM EE M AE CGS MTS SI
Acceleration (a) ft/s2 m/s2 ft/s2 m/s2 ft/s2 Gal m/s2 m/s2
Mass (m) slug hyl lbm kg lb g t kg
Force (F) lb kp lbF kp pdl dyn sn N
Pressure (p) lb/in2 at PSI atm pdl/ft2 Ba pz Pa

See also

References

  1. ^ "Table 3. Coherent derived units in the SI with special names and symbols". The International System of Units (SI). International Bureau of Weights and Measures. 2006. http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html. 
  2. ^ http://www.convertunits.com/from/kilonewtons/to/kilograms-force
  3. ^ Lindeburg, Michael, Civil Engineering Reference Manual for the PE Exam 
  4. ^ Wurbs, Ralph A, Fort Hood Review Sessions for Professional Engineering Exam, http://engineeringregistration.tamu.edu/tapedreviews/Fluids-PE/PDF/Fluids-PE.pdf, retrieved October 26, 2011 
Base units
Ampere · Candela · Kelvin · Kilogram · Metre · Mole · Second
Derived units
Becquerel · Coulomb · degree Celsius · Farad · Gray · Henry · Hertz · Joule · Katal · Lumen · Lux · Newton · Ohm · Pascal · Radian · Siemens · Sievert · Steradian · Tesla · Volt · Watt · Weber
Accepted for use
with SI
See also
Book:International System of Units  · Category:SI base units