Newton
The newton (symbol: N) is the SI derived unit of force, named after 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 accelerate a mass of one kilogram at a rate of one meter per second per second. In dimensional analysis, F=ma, multiplying m (kg) by a (m/s2), the dimension for 1 newton unit is therefore:
Examples
- 1N is the force of Earth's gravity on an object with a mass of about 102g or 1/9.81 kg (such as a small apple).
- On Earth's surface, a mass of 1kg exerts a force of approximately 9.8N [down] (or 1.0kilogram-force; 1 kgf=9.80665 N by definition). The approximation of 1kg corresponding to 10N is sometimes used as a rule of thumb in everyday life and in engineering.
- The force of Earth's gravity on a human being with a mass of 70kg is approximately 686N.
- The product of force and distance is mechanical work. Thus, in SI units, a force of 1N exerted over a distance of 1m 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 = 1J (joule), the SI unit of energy.
- It is common to see forces expressed in kilonewtons or kN, where 1kN= 1,000N.
- An amusing rule of thumb to help remember the Newton: On earth, a N is equivalent to ~100 g; coincidentally, this is about the mass of an apple. So, you can think of a N as getting hit on the head with an apple.
Conversion factors
Units of Force
| |
newton (SI unit) |
dyne |
Kilogram-force, |
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 |
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 |
kilopond |
pound-force |
kilopond |
poundal |
newton |
Note: This article uses material from the Wikipedia article Newton (unit) that was accessed on April 7, 2010. The Author(s) and Topic Editor(s) associated with this article may have significantly modified the content derived from Wikipedia with original content or with content drawn from other sources. All content from Wikipedia has been reviewed and approved by those Author(s) and Topic Editor(s), and is subject to the same peer review process as other content in the EoE. The current version of the Wikipedia article may differ from the version that existed on the date of access. See the EoE’s Policy on the Use of Content from Wikipedia for more information.
