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The newton (symbol: N) is the SI derived unit of force, named after Isaac Newton in recognition of his work on classical mechanics.

Contents

Definition

The newton is the unit of force derived in the SI system; it is equal to the amount of force required to give a mass of one kilogram an acceleration of one meter per second squared. Algebraically:

1N = 1kg.m⁄s2

{\rm 1~N = 1~\frac{kg\cdot m}{s^2}}.1

Examples

  • 1 N is the force of Earth's gravity on an object with a mass of about 102 g (1⁄9.8 kg) (such as a small apple).
  • On Earth's surface, a mass of 1 kg exerts a force of approximately 9.80665 N [down] (or 1 kgf). The approximation of 1 kg corresponding to 10 N is sometimes used as a rule of thumb in everyday life and in engineering.
  • The decanewton (daN) = 10 N is increasingly used when specifying load bearing capacity of items such as ropes and anti-vibration mounts because it is approximately equivalent to the more familiar non-SI unit of force, the kgf.
  • The force of Earth's gravity on a human being with a mass of 70 kg is approximately 687 N.
  • The dot product of force and distance is mechanical work. Thus, in SI units, a force of 1 N exerted over a distance of 1 m is 1 N·m of work. The Work-Energy Theorem states that the work done on a body is equal to the change in energy of the body. 1 N·m = 1 J (joule), the SI unit of energy.
  • It is common to see forces expressed in kilonewtons or kN, where 1 kN = 1 000 N.
  • A tonne (metric ton)=(1 000 kg) exerts a force of 9.80665 kN (or 1 000 kgf) under standard gravity conditions on Earth.

Notes

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
System Gravitational Engineering Absolute
Force (F) F = m·a F = m·a/gc = w·a/g F = m·a
Weight (w) w = m·g w = m·g/gc ≈ m w = m·g
Units English Metric English Metric English Metric
Acceleration (a) ft/s2 m/s2 ft/s2 m/s2 ft/s2 m/s2
Mass (m) slug hyl pound-mass kilogram pound kilogram
Force (F) pound newton pound-force newton poundal newton

1 kp = 9.80665 N. kp is kilopond 1 kilopond was the measure of 1 kilogram on Earth.

in 1960 this measure was changed to newtons

1 kg on the surface of the Earth weighs 9.8 N, because 1 kg × 9.8 m/s^2 = 9.8 N.

References

  1. ^ Serway and Jewett (2008). Physics for Scientists and Engineers

http://www.sengpielaudio.com/calculator-forceunits.htm

See also
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