Kilogram-force


The kilogram-force, or kilopond, is a gravitational metric unit of force. It is equal to the magnitude of the force exerted on one kilogram of mass in a gravitational field. Therefore, one kilogram-force is by definition equal to. Similarly, a gram-force is, and a milligram-force is.
Kilogram-force is a non-standard unit and is classified in the International System of Units as a unit that is unacceptable for use with SI.

History

The gram-force and kilogram-force were never well-defined units until the CGPM adopted a standard acceleration of gravity of 980.665 cm/s2 for this purpose in 1901, though they had been used in low-precision measurements of force before that time.
The kilogram-force has never been a part of the International System of Units, which was introduced in 1960. The SI unit of force is the newton.
Prior to this, the unit was widely used in much of the world and it is still in use for some purposes, for example, it is used for tension of bicycle spokes, for informal references to pressure in kilograms per square centimeter which is the technical atmosphere and very close to 1 bar and the standard atmosphere, for the draw weight of bows in archery, and to define the "metric horsepower" as 75 metre-kiloponds per second. In addition, kilograms force is the standard unit used for Vickers hardness testing.
In 1940s Germany, the thrust of a rocket engine was measured in kilograms-force, in the Soviet Union it remained the primary unit for thrust in the Russian space program until at least the late 1980s. Kilogram-force is still used today in China and the European Space Agency.
The term "kilopond" has been declared obsolete.

Related units

The tonne-force, metric ton-force, megagram-force, and megapond are each 1000 kilograms-force.
The decanewton or dekanewton, 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.