Gravitational metric system
Encyclopedia
In the gravitational metric system(s) the base unit of force is not normalised to one mass unit (gram
or kilogram
) times one length unit (metre
or centimetre) per time unit squared (second) as in the SI
, but it depends on a selected or locally measured gravitational constant gn. This constant is usually set to an acceleration of 9.80665 m/s² on Earth. Other derived units inherit this factor. Sometimes alternately the base unit of mass is the one carrying the constant.
Where the difference between weight and mass is not important or not understood, gravitational units are still common despite adoption of the SI, an absolute metric system
.
(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 · gn = 9.80665 g·m/s² = 980.665 g·cm/s² = 980.665 dyn
1 kp = 1 kgf := 1 kg · gn = 9.80665 kg·m/s² = 980 665 g·cm/s²
1 TME := 1 kp / 1 m/s² = 1 kp·s²/m = 9.806 65 kg
1 hyl := 1 kp·s²/m = 9.806 65 kg or
1 hyl (alternate definition - mgfs) := 1 p·s²/m = 9.806 65 g
(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 × gn kg/m² = 98 066.5 kg/(m·s²) = 98.066 5 kPa
”, but usually the symbol of the kilopond-metre is written without the middle dot.
1 kpm := 1 kp·m = gn kg·m = 9.806 65 kg·m²/s² = 9.806 65 J
, which was defined as the power required to raise a mass of 1 quintal
(1 q = 100 kg) at a velocity of 1 m/s. The German or metric horsepower
(PS, Pferdestärke) is arbitrarily selected to be three quarters thereof.
1 pq := 1 qf·m/s = 100 kp·m/s = 100 × gn kg·m/s = 980.665 kg·m²/s³ = 0.980 665 kW
1 PS := pq = 75 kp·m/s = 75 × gn kg·m/s = 735.498 75 kg·m²/s³ = 0.735 498 75 kW
Gram
The gram is a metric system unit of mass....
or kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
) times one length unit (metre
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
or centimetre) per time unit squared (second) as in the SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
, but it depends on a selected or locally measured gravitational constant gn. This constant is usually set to an acceleration of 9.80665 m/s² on Earth. Other derived units inherit this factor. Sometimes alternately the base unit of mass is the one carrying the constant.
Where the difference between weight and mass is not important or not understood, gravitational units are still common despite adoption of the SI, an absolute metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
.
Force
In English contexts the unit of force is usually formed by simply appending “force” to the unit of mass, thus gram-force (gf) or kilogram-forceKilogram-force
A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
(kgf), which follows the tradition of pound-force
Pound-force
The pound force is a unit of force in some systems of measurement including English engineering units and British gravitational units.- Definitions :...
(lbf). In other, international contexts the special name pond (p) or kilopond (kp) respectively is more frequent.
1 p = 1 gf := 1 g · gn = 9.80665 g·m/s² = 980.665 g·cm/s² = 980.665 dyn
Dyne
In physics, the dyne is a unit of force specified in the centimetre-gram-second system of units, a predecessor of the modern SI. One dyne is equal to exactly 10 µN...
1 kp = 1 kgf := 1 kg · gn = 9.80665 kg·m/s² = 980 665 g·cm/s²
Mass
The hyl, metric slug (mug), or TME (German: technische Masseneinheit, technical mass unit), is the mass that accelerates at 1 m/s² under a force of 1 kgf. The hyl has also been used as the unit of mass in a metre-gram force-second (mgfs) system.1 TME := 1 kp / 1 m/s² = 1 kp·s²/m = 9.806 65 kg
1 hyl := 1 kp·s²/m = 9.806 65 kg or
1 hyl (alternate definition - mgfs) := 1 p·s²/m = 9.806 65 g
Pressure
The (only) gravitational unit of pressure is the technical atmosphereTechnical atmosphere
A technical atmosphere is a non-SI unit of pressure equal to one kilogram-force per square centimeter.The symbol "at" clashes with that of the katal , the SI unit of catalytic activity; a kilotechnical atmosphere would have the symbol "kat", indistinguishable from the symbol for the katal...
(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 × gn kg/m² = 98 066.5 kg/(m·s²) = 98.066 5 kPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
Energy
There is no dedicated name for the unit of energy, “metre” is simply appended to “kilopondKilogram-force
A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
”, but usually the symbol of the kilopond-metre is written without the middle dot.
1 kpm := 1 kp·m = gn 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 ponceletPoncelet
The poncelet is an obsolete unit of power, once used in France and replaced by cheval vapeur . The unit was named after Jean-Victor Poncelet....
, which was defined as the power required to raise a mass of 1 quintal
Quintal
Quintal may refer to:* Quintal , a unit of mass* Quartal and quintal harmony in music* Quintal, Haute-Savoie, a commune of the Haute-Savoie département in France* Stéphane Quintal, NHL ice hockey player...
(1 q = 100 kg) at a velocity of 1 m/s. The German or metric horsepower
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
(PS, Pferdestärke) is arbitrarily selected to be three quarters thereof.
1 pq := 1 qf·m/s = 100 kp·m/s = 100 × gn kg·m/s = 980.665 kg·m²/s³ = 0.980 665 kW
1 PS := pq = 75 kp·m/s = 75 × gn kg·m/s = 735.498 75 kg·m²/s³ = 0.735 498 75 kW