The gravitational metric system (original French term ) is a non-standard system of units, which does not comply with the International System of Units (SI). It is built on the three base quantities length,

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, ...

and force with

base units A base unit (also referred to as a fundamental unit) is a unit adopted for measurement of a '' base quantity''. A base quantity is one of a conventionally chosen subset of physical quantities, where no quantity in the subset can be expressed in ter ...

metre The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...

, second and kilopond respectively. Internationally used abbreviations of the system are MKpS, MKfS or MKS (from French or ). However, the abbreviation MKS is also used for the MKS system of units, which, like the SI, uses

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...

in kilogram as a base unit.

Disadvantages

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 In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

of 45 degrees, since 1902 via the standard gravity of . Further disadvantages are inconsistencies in the definition of derived units such as

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are t ...

(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 1 January 1978, when for legal purposes the SI unit system was adopted. A kilopond can be converted to the SI unit newton by multiplication with the standard acceleration ''g''_n: :1 kp = ''g''_n ⋅ 1 kg = =

Units

Force

In English contexts the unit of force is usually formed by simply appending the suffix "force" to the name of the unit of mass, thus ''gram-force'' (gf) or ''

kilogram-force The kilogram-force (kgf or kgF), or kilopond (kp, from la, pondus, lit=weight), is a non-standard gravitational metric unit of force. It does not comply with the International System of Units (SI) and is deprecated for most uses. The kilogram- ...

'' (kgf), which follows the tradition of pound-force (lbf). In other, international, contexts the special name ''pond'' (p) or ''kilopond'' (kp) respectively is more frequent. ; 1 p = 1 gf := 1 g ⋅ ''g''_n = 9.80665 g⋅m/s² = 980.665 g⋅cm/s² = 980.665 dyn ; 1 kp = 1 kgf := 1 kg ⋅ ''g''_n = 9.80665 kg⋅m/s² = 980665 g⋅cm/s²

Mass

The hyl, metric slug (mug), or TME (german: technische Masseneinheit, lit=technical mass unit), is the mass that accelerates at 1 m/s² under a force of 1 kgf. The unit, long obsolete, has also been used as the unit of mass in a metre–gram-force–second (mgfs) system.metre–kilogram-force–second systems of units
/ref> ; 1 TME := 1 kp / 1 m/s² = 1 kp⋅s²/m = ; 1 hyl := 1 kp⋅s²/m = ''or'' ; 1 hyl (alternate definition – mgfs) := 1 p⋅s²/m =

Pressure

The gravitational unit of pressure is the

technical atmosphere Technical may refer to: * Technical (vehicle), an improvised fighting vehicle * Technical analysis, a discipline for forecasting the future direction of prices through the study of past market data * Technical drawing, showing how something is co ...

(at). It is the gravitational force of one kilogram, i.e. 1 kgf, exerted on an area of one square centimetre. ; 1 at := 1 kp/cm² = 10 000 × ''g''_n kg/m² = 98 066.5 kg/(m⋅s²) = 98.066 5 kPa

Energy

There is no dedicated name for the unit of energy, "metre" is simply appended to " kilopond", but usually the symbol of the kilopond-metre is written without the middle dot. ; 1 kpm := 1 kp⋅m = ''g''_n kg⋅m = 9.806 65 kg⋅m²/s² = 9.806 65 J

Power

In 19th-century France there was as a unit of power, the

poncelet The poncelet (symbol p) is an obsolete unit of power, once used in France and replaced by (ch, metric horsepower). The unit was named after Jean-Victor Poncelet.François Cardarelli, ''Encyclopaedia of Scientific Units, Weights and Measures: The ...

, which was defined as the power required to raise a mass of 1

quintal The quintal or centner is a historical unit of mass in many countries which is usually defined as 100 base units, such as pounds or kilograms. It is a traditional unit of weight in France, Portugal, and Spain and their former colonies. It is com ...

(1 q = 100 kg) at a velocity of 1 m/s. The German or metric

(PS, ''Pferdestärke'') is arbitrarily selected to be three quarters thereof. ; 1 p_q := 1 q_f⋅m/s = 100 kp⋅m/s = 100 × ''g''_n kg⋅m/s = 980.665 kg⋅m²/s³ = 0.980 665 kW ; 1 PS := p_q = 75 kp⋅m/s = 75 × ''g''_n kg⋅m/s = 735.498 75 kg⋅m²/s³ = 0.735 498 75 kW

References

{{systems of measurement Systems of units Gravitational metric system