Gravitational metric system
The gravitational metric system (original French term Système des Méchaniciens) is a non-standard system of units, that does not comply with the International System of Units (SI). It is built on the three base quantities length, time and force with base units metre, second and kilopond respectively. Internationally used abbreviations of the system are MKpS, MKfS or MKS (from French mètre-kilogramme-poids-seconde or mètre-kilogramme-force-seconde). However, the abbreviation MKS is also used for the MKS system of units, which, like the SI, uses mass in kilogram as a base unit.
Nowadays, the mass as a property of an object and its weight, which depends on the gravity of the earth at its position are strictly distinguished. However historically, the kilopond was also called kilogram, and only later the kilogram-mass (today's kilogram) was separated from the kilogram-force (today's kilopond). A kilopond originally referred to the weight of a mass of one kilogram. Since the gravitational acceleration on the surface of the earth can differ, one gets different values for the unit kilopond and its derived units at different locations. To avoid this, the kilopond was first defined at sea-level and a latitude of 45 degrees, since 1902 via the Standard gravity of 9.80665 m/s2.
Further disadvantages are inconsistencies in the definition of derived units such as horsepower (1 PS = 75 kp·m/s) and the missing link to electric, magnetic or thermodynamic units.
In Germany, the kilopond lost its legal status as a unit of force on the first of January 1978 and is replaced by SI units. A kilopond can be converted to the SI unit Newton by multiplication with the standard acceleration :
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