Newton
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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.
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[edit] 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:
[edit] 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 9.81 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.
[edit] Notes
| 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. | |||||
| 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 | kilopond | pound-force | kilopond | poundal | newton |
[edit] References
- Halliday, Resnick and Walker Fundamentals of Physics, John Wiley & Sons ISBN 0471470619
[edit] 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.
