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

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:

Examples

  • 1 N is the force of earth's gravity on an object with a mass of about 102 g (19.8 kg) (such as a small apple).
  • On Earth's surface, a mass of 1 kg exerts a force of approximately 9.81 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, being 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 scalar product of force and distance is energy. Thus, in SI units, a force of 1 N exerted over a distance of 1 m is 1 N·m = 1 joule, the SI unit of energy.
  • Because a newton is a small force, it is common to see forces expressed in kilonewtons or kN, where 1 kN = 1 000 N.
  • A metric tonne (1 000 kg) exerts a force of 9.8 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.

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References

  • Halliday, Resnick and Walker Fundamentals of Physics, John Wiley & Sons ISBN 0471470619

See also

  • Joule, the SI unit of energy, equivalent to 1 newton exerted over a distance of 1 meter.
  • Pascal, the SI unit of pressure, equivalent to 1 newton acting on an area of 1 square meter.
  • Kilogram-force, the force exerted by Earth's gravity on one kilogram of mass.

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