| kilogram-force | |
|---|---|
| Unit system | Gravitational metric system |
| Unit of | Force |
| Symbol | kgf |
| Conversions | |
| 1 kgfin ... | ... is equal to ... |
| SI units | 9.806650 N |
| CGS units | 980,665.0 dyn |
| British Gravitational units | 2.204623 lbf |
| Absolute English units | 70.93164 pdl |
Thekilogram-force (kgf orkgF), orkilopond (kp, fromLatin:pondus,lit. 'weight'), is a non-standardgravitational metric unit offorce. It is not accepted for use with the International System of Units (SI)[1] and is deprecated for most uses.[citation needed] The kilogram-force is equal to the magnitude of the force exerted on onekilogram ofmass in a9.80665 m/s2 gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth).[2] That is, it is theweight of a kilogram under standard gravity. One kilogram-force is defined as9.80665 N.[3][4] Similarly, a gram-force is9.80665 mN, and a milligram-force is9.80665 μN.
The gram-force and kilogram-force were never well-defined units until theCGPM adopted astandard acceleration of gravity of 9.80665 m/s2 for this purpose in 1901,[5] though they had been used in low-precision measurements of force before that time. Even then, the proposal to define kilogram-force as a standard unit of force was explicitly rejected.[6] Instead, thenewton was proposed in 1913[7] and accepted in 1948.[8]The kilogram-force has never been a part of theInternational System of Units (SI), which was introduced in 1960. The SI unit of force is thenewton.
Prior to this, the units were widely used in much of the world. They are still in use for some purposes; for example, they are used to specify tension of bicyclespokes,[9]draw weight of bows inarchery, and tensile strength ofelectronicsbond wire,[10] for informal references to pressure (as the technically incorrectkilogram per square centimetre, omitting-force, the kilogram-force per square centimetre being thetechnical atmosphere, the value of which is very near those of both thebar and thestandard atmosphere), and to define the "metric horsepower" (PS) as 75 metre-kiloponds per second.[3] In addition, the kilogram force was the standard unit used forVickers hardness testing.[11]
| Base | Force | Weight | Mass | ||
|---|---|---|---|---|---|
| 2nd law of motion | m =F/a | F =W ⋅a/g | F =m ⋅a | ||
| System | GM | M | CGS | MTS | SI |
| Acceleration (a) | m/s2 | m/s2 | Gal | m/s2 | m/s2 |
| Mass (m) | hyl | kilogram | gram | tonne | kilogram |
| Force (F), weight (W) | kilopond | kilopond | dyne | sthène | newton |
| Pressure (p) | technical atmosphere | standard atmosphere | barye | pieze | pascal |
In 1940s, Germany, the thrust of a rocket engine was measured in kilograms-force,[citation needed] in the Soviet Union it remained the primary unit for thrust in the Russian space program until at least the late 1980s.[citation needed] Dividing the thrust in kilograms-force on the mass of an engine or a rocket in kilograms conveniently gives thethrust to weight ratio, dividing the thrust on propellant consumption rate (mass flow rate) in kilograms per second gives thespecific impulse in seconds.
The term "kilopond" has been declared obsolete.[14]
Thetonne-force,metric ton-force,megagram-force, andmegapond (Mp) are each 1000 kilograms-force.
Thedecanewton ordekanewton (daN), exactly 10 N, is used in some fields as an approximation to the kilogram-force, because it is close to the 9.80665 N of 1 kgf.
The gram-force is1⁄1000 of a kilogram-force.
| newton | dyne | kilogram-force, kilopond | pound-force | poundal | |
|---|---|---|---|---|---|
| 1 N | ≡ 1 kg⋅m/s2 | = 105 dyn | ≈ 0.10197 kgf | ≈ 0.22481 lbF | ≈ 7.2330 pdl |
| 1 dyn | = 10−5 N | ≡ 1 g⋅cm/s2 | ≈ 1.0197×10−6 kgf | ≈ 2.2481×10−6 lbF | ≈ 7.2330×10−5 pdl |
| 1 kgf | = 9.80665 N | = 980665 dyn | ≡ gn × 1 kg | ≈ 2.2046 lbF | ≈ 70.932 pdl |
| 1 lbF | ≈ 4.448222 N | ≈ 444822 dyn | ≈ 0.45359 kgf | ≡ gn × 1 lb | ≈ 32.174 pdl |
| 1 pdl | ≈ 0.138255 N | ≈ 13825 dyn | ≈ 0.014098 kgf | ≈ 0.031081 lbF | ≡ 1 lb⋅ft/s2 |
| The value ofgn (9.80665 m/s2) as used in the official definition of the kilogram-force is used here for all gravitational units. | |||||
The recommended tension for spokes in bicycle wheels can be as low as 80 Kilograms force (Kfg) and as high as 230 Kilograms force. Author=Park Tool
Breaking load (BL): The strength of a wire and its actual force (usually given in grams, grams-force, mN, etc.) required to break a particular wire in a tensile pull. It is not tensile strength, which by definition is the force per unit area.
In the past the units for Vickers hardness were kg/mm2; in Table 12.6 we use the SI units of GPa.
