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59-447: A tetrathlon (from the numerical prefix " tetra- " meaning four) is a team competition organized by Pony Clubs for its members. It is a variant of the modern pentathlon , without fencing. Thus, it comprises the four disciplines of shooting , swimming , riding , and running . Ideally, teams consist of four members from one pony club competing against several teams from rival clubs. Competitions are usually held over two days during

118-466: A coherent system the units of force , energy , and power are chosen so that the equations hold without the introduction of unit conversion factors. Once a set of coherent units has been defined, other relationships in physics that use this set of units will automatically be true. Therefore, Einstein 's mass–energy equation , E = mc , does not require extraneous constants when expressed in coherent units. The CGS system had two units of energy,

177-841: A commission to implement this new standard alone, and in 1799, the new system was launched in France. The units of the metric system, originally taken from observable features of nature, are now defined by seven physical constants being given exact numerical values in terms of the units. In the modern form of the International System of Units (SI), the seven base units are: metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for temperature, candela for luminous intensity and mole for amount of substance. These, together with their derived units, can measure any physical quantity. Derived units may have their own unit name, such as

236-595: A decimal multiple of it; and the unit of mass should be the gram or a decimal multiple of it. Metric systems have evolved since the 1790s, as science and technology have evolved, in providing a single universal measuring system. Before and in addition to the SI, other metric systems include: the MKS system of units and the MKSA systems, which are the direct forerunners of the SI; the centimetre–gram–second (CGS) system and its subtypes,

295-450: A fourth base unit, the various anomalies in electromagnetic systems could be resolved. The metre–kilogram–second– coulomb (MKSC) and metre–kilogram–second– ampere (MKSA) systems are examples of such systems. The metre–tonne–second system of units (MTS) was based on the metre, tonne and second – the unit of force was the sthène and the unit of pressure was the pièze . It was invented in France for industrial use and from 1933 to 1955

354-406: A marginal position. There is also an international set of metric prefixes , which are used in the world's standard measurement system . In the following prefixes, a final vowel is normally dropped before a root that begins with a vowel, with the exceptions of bi-, which is extended to bis- before a vowel; among the other monosyllables , du- , di- , dvi- , and tri- , never vary. Words in

413-474: A metre. This is unlike older systems of units in which the ratio between the units for longer and shorter distances varied: there are 12 inches in a foot, but the number of 5,280 feet in a mile is not a power of 12. For many everyday applications, the United States has resisted the adoption of a decimal-based system, continuing to use "a conglomeration of basically incoherent measurement systems ". In

472-618: A multiple of 10 rather than multiplication by it. Several common-use numerical prefixes denote vulgar fractions . Words containing non-technical numerical prefixes are usually not hyphenated. This is not an absolute rule, however, and there are exceptions (for example: quarter-deck occurs in addition to quarterdeck ). There are no exceptions for words comprising technical numerical prefixes, though. Systematic names and words comprising SI prefixes and binary prefixes are not hyphenated, by definition. Nonetheless, for clarity, dictionaries list numerical prefixes in hyphenated form, to distinguish

531-399: A numerical prefix need not be related to the root language of the word that it prefixes. Some words comprising numerical prefixes are hybrid words . In certain classes of systematic names, there are a few other exceptions to the rule of using Greek-derived numerical prefixes. The IUPAC nomenclature of organic chemistry , for example, uses the numerical prefixes derived from Greek, except for

590-437: A range of 7 or 10 metres depending on their age. Younger (minimus) competitors are allowed to use two hands while older competitors must use only one. Ten shots are fired under timed conditions with a maximum of four seconds allowed per shot. Competitors are required to complete a show jumping or cross-country course including a number of fences (jumps) under timed conditions depending on the weather. If ground conditions are bad

649-420: A representative quantity is defined as a base unit of measure. The definition of base units has increasingly been realised in terms of fundamental natural phenomena, in preference to copies of physical artefacts. A unit derived from the base units is used for expressing quantities of dimensions that can be derived from the base dimensions of the system—e.g., the square metre is the derived unit for area, which

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708-406: A second greater than 1; the non-SI units of minute , hour and day are used instead. On the other hand, prefixes are used for multiples of the non-SI unit of volume, the litre (l, L) such as millilitres (ml). Each variant of the metric system has a degree of coherence—the derived units are directly related to the base units without the need for intermediate conversion factors. For example, in

767-480: A standard without reliance on an artefact held by another country. In practice, such realisation is done under the auspices of a mutual acceptance arrangement . In 1791 the commission originally defined the metre based on the size of the earth, equal to one ten-millionth of the distance from the equator to the North Pole. In the SI, the standard metre is now defined as exactly 1 ⁄ 299 792 458 of

826-411: Is derived from length. These derived units are coherent , which means that they involve only products of powers of the base units, without any further factors. For any given quantity whose unit has a name and symbol, an extended set of smaller and larger units is defined that are related by factors of powers of ten. The unit of time should be the second ; the unit of length should be either the metre or

885-470: Is expressed in g/cm , force expressed in dynes and mechanical energy in ergs . Thermal energy was defined in calories , one calorie being the energy required to raise the temperature of one gram of water from 15.5 °C to 16.5 °C. The meeting also recognised two sets of units for electrical and magnetic properties – the electrostatic set of units and the electromagnetic set of units. The CGS units of electricity were cumbersome to work with. This

944-633: Is in turn from pro- and the Greek word for fat), and butane (from butyl , which is in turn from butyric , which is in turn from the Latin word for butter). Metric system The metric system is a decimal -based system of measurement . The current international standard for the metric system is the International System of Units (Système international d'unités or SI), in which all units can be expressed in terms of seven base units:

1003-597: The Avogadro number number of specified molecules, was added along with several other derived units. The system was promulgated by the General Conference on Weights and Measures (French: Conférence générale des poids et mesures – CGPM) in 1960. At that time, the metre was redefined in terms of the wavelength of a spectral line of the krypton-86 atom (krypton-86 being a stable isotope of an inert gas that occurs in undetectable or trace amounts naturally), and

1062-538: The CGS electrostatic (cgs-esu) system, the CGS electromagnetic (cgs-emu) system, and their still-popular blend, the Gaussian system ; the metre–tonne–second (MTS) system; and the gravitational metric systems , which can be based on either the metre or the centimetre, and either the gram, gram-force, kilogram or kilogram-force. The SI has been adopted as the official system of weights and measures by nearly all nations in

1121-529: The International System of Units (SI). The International System of Units is the modern metric system. It is based on the metre–kilogram–second–ampere (MKSA) system of units from early in the 20th century. It also includes numerous coherent derived units for common quantities like power (watt) and irradience (lumen). Electrical units were taken from the International system then in use. Other units like those for energy (joule) were modelled on those from

1180-570: The Mètre des Archives and Kilogramme des Archives (or their descendants) as their base units, but differing in the definitions of the various derived units. In 1832, Gauss used the astronomical second as a base unit in defining the gravitation of the Earth, and together with the milligram and millimetre, this became the first system of mechanical units . He showed that the strength of a magnet could also be quantified in terms of these units, by measuring

1239-551: The Practical System of Electric Units , or QES (quad–eleventhgram–second) system, was being used. Here, the base units are the quad, equal to 10  m (approximately a quadrant of the Earth's circumference), the eleventhgram, equal to 10  g , and the second. These were chosen so that the corresponding electrical units of potential difference, current and resistance had a convenient magnitude. In 1901, Giovanni Giorgi showed that by adding an electrical unit as

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1298-706: The cardinal catgegory are cardinal numbers , such as the English one , two , three , which name the count of items in a sequence. The multiple category are adverbial numbers, like the English once , twice , thrice , that specify the number of events or instances of otherwise identical or similar items. Enumeration with the distributive catgegory originally was meant to specify one each , two each or one by one , two by two , etc., giving how many items of each type are desired or had been found, although distinct word forms for that meaning are now mostly lost. The ordinal catgegory are based on ordinal numbers such as

1357-486: The erg that was related to mechanics and the calorie that was related to thermal energy ; so only one of them (the erg) could bear a coherent relationship to the base units. Coherence was a design aim of SI, which resulted in only one unit of energy being defined – the joule . Maxwell's equations of electromagnetism contained a factor of 1 / ( 4 π ) {\displaystyle 1/(4\pi )} relating to steradians , representative of

1416-437: The metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd). These can be made into larger or smaller units with the use of metric prefixes . SI derived units are named combinations – such as the hertz (cycles per second), newton (kg⋅m/s ), and tesla (1 kg⋅s ⋅A ) – or a shifted scale, in the case of degrees Celsius . Certain units have been officially accepted for use with

1475-455: The metre, kilogram, second system of units , though the definitions of the fundamental SI units have been changed to depend only on constants of nature. Other metric system variants include the centimetre–gram–second system of units , the metre–tonne–second system of units , and the gravitational metric system . Each of these has some unique named units (in addition to unaffiliated metric units ) and some are still in use in certain fields. In

1534-448: The watt (J/s) and lux (cd/m ), or may just be expressed as combinations of base units, such as velocity (m/s) and acceleration (m/s ). The metric system was designed to have properties that make it easy to use and widely applicable, including units based on the natural world, decimal ratios, prefixes for multiples and sub-multiples, and a structure of base and derived units. It is a coherent system , derived units were built up from

1593-442: The English first , second , third , which specify position of items in a sequence. In Latin and Greek, the ordinal forms are also used for fractions for amounts higher than 2; only the fraction ⁠ 1  / 2 ⁠ has special forms. The same suffix may be used with more than one category of number, as for example the orginary numbers second ary and terti ary and the distributive numbers bi nary and ter nary . For

1652-452: The SI . Some of these are decimalised, like the litre and electronvolt , and are considered "metric". Others, like the astronomical unit are not. Ancient non-metric but SI-accepted multiples of time ( minute and hour ) and angle ( degree , arcminute , and arcsecond ) are sexagesimal (base 60). The "metric system" has been formulated in a number of different ways over the centuries. The SI system originally derived its terminology from

1711-528: The United Kingdom. In the United States, competitors swim 50 yards/meters, 100 yards/meters, or 200 yards/meters depending on their age and/or division of competition. Swimming is usually the first sport that takes place in a tetrathlon because it makes the participants the most tired, due to the amount of force that the participants have to exert while swimming. Competitors are required to shoot at stationary targets using .177 calibre air pistols from

1770-436: The base units using logical rather than empirical relationships while multiples and submultiples of both base and derived units were decimal-based and identified by a standard set of prefixes . The metric system is extensible, and new derived units are defined as needed in fields such as radiology and chemistry. For example, the katal , a derived unit for catalytic activity equivalent to one mole per second (1 mol/s),

1829-513: The common inheritance of Greek and Latin roots across the Romance languages , the import of much of that derived vocabulary into non-Romance languages (such as into English via Norman French ), and the borrowing of 19th and 20th century coinages into many languages, the same numerical prefixes occur in many languages. Numerical prefixes are not restricted to denoting integers. Some of the SI prefixes denote negative powers of 10, i.e. division by

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1888-402: The competitor may not be timed. The size of the fences range from 2 foot 6 inches to 3 foot 6 inches depending on the age and competitive level of the competitors. Each course also includes a hazard section, containing a swinging gate which must be opened and closed while remaining on horseback, and a slip rail , through which riders lead their horse after dismounting. This element of

1947-546: The course is timed and is similar to that found in hunter trials . Competitors run cross-country which may include obstacles under timed conditions. Distances are 1,000 metres, 1,500 metres and 3,000 metres depending upon age category in the United Kingdom, or 500 meters, 1000 meters, 2000 meters, or 3000 meters in the United States. Runners do not run against each other directly as in a marathon or race; instead start times are staggered at one-minute intervals. Tetrathletes may also compete in triathlons (not to be confused with

2006-463: The definition of the International System of Units (SI) in the mid-20th century, under the oversight of an international standards body. Adopting the metric system is known as metrication . The historical evolution of metric systems has resulted in the recognition of several principles. A set of independent dimensions of nature is selected, in terms of which all natural quantities can be expressed, called base quantities. For each of these dimensions,

2065-421: The distance that light travels in a second . The metre can be realised by measuring the length that a light wave travels in a given time, or equivalently by measuring the wavelength of light of a known frequency. The kilogram was originally defined as the mass of one cubic decimetre of water at 4 °C, standardised as the mass of a man-made artefact of platinum–iridium held in a laboratory in France, which

2124-401: The early days, multipliers that were positive powers of ten were given Greek-derived prefixes such as kilo- and mega- , and those that were negative powers of ten were given Latin-derived prefixes such as centi- and milli- . However, 1935 extensions to the prefix system did not follow this convention: the prefixes nano- and micro- , for example have Greek roots. During the 19th century

2183-425: The fact that electric charges and magnetic fields may be considered to emanate from a point and propagate equally in all directions, i.e. spherically. This factor made equations more awkward than necessary, and so Oliver Heaviside suggested adjusting the system of units to remove it. The basic units of the metric system, as originally defined, represented common quantities or relationships in nature. They still do –

2242-428: The games, rosettes are awarded to the top scores in each discipline, for the highest overall scores, and for the best team performances in each of the age and sex categories. Competitors are required to swim freestyle a distance appropriate for their age and the level at which they are competing. Swimming is scored on a grid of age, level and time. Competitors have to swim for 2 or 3 minutes depending on their age, in

2301-449: The host club, local farmers, landowners, and parents. There are three age categories, known as minimus, (8 to 11), junior (12 to 14) and senior (15 to 21). Boys and girls compete together. There is no minimum qualification standard to compete, but contests are only open to active pony club members (in the US this means those who have attended at least three rallies that year). At the end of

2360-500: The hundreds, there are competing forms: Those in -gent- , from the original Latin, and those in -cent- , derived from centi- , etc. plus the prefixes for 1 through 9 . Many of the items in the following tables are not in general use, but may rather be regarded as coinages by individuals. In scientific contexts, either scientific notation or SI prefixes are used to express very large or very small numbers, and not unwieldy prefixes. ( but hybrid hexadecimal ) Because of

2419-421: The kilogram in terms of fundamental constants. A base quantity is one of a conventionally chosen subset of physical quantities, where no quantity in the subset can be expressed in terms of the others. A base unit is a unit adopted for expressing a base quantity. A derived unit is used for expressing any other quantity, and is a product of powers of base units. For example, in the modern metric system, length has

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2478-419: The metric system, multiples and submultiples of units follow a decimal pattern. A common set of decimal-based prefixes that have the effect of multiplication or division by an integer power of ten can be applied to units that are themselves too large or too small for practical use. The prefix kilo , for example, is used to multiply the unit by 1000, and the prefix milli is to indicate a one-thousandth part of

2537-510: The modern precisely defined quantities are refinements of definition and methodology, but still with the same magnitudes. In cases where laboratory precision may not be required or available, or where approximations are good enough, the original definitions may suffice. Basic units: metre , kilogram , second , ampere , kelvin , mole , and candela for derived units, such as Volts and Watts, see International System of Units . A number of different metric system have been developed, all using

2596-430: The older CGS system, but scaled to be coherent with MKSA units. Two additional base units – the kelvin , which is equivalent to degree Celsius for change in thermodynamic temperature but set so that 0 K is absolute zero , and the candela , which is roughly equivalent to the international candle unit of illumination – were introduced. Later, another base unit, the mole , a unit of amount of substance equivalent to

2655-607: The original, called the IPK . It became apparent that either the IPK or the replicas or both were deteriorating, and are no longer comparable: they had diverged by 50 μg since fabrication, so figuratively, the accuracy of the kilogram was no better than 5 parts in a hundred million or a relative accuracy of 5 × 10 . The revision of the SI replaced the IPK with an exact definition of the Planck constant as expressed in SI units, which defines

2714-606: The oscillations of a magnetised needle and finding the quantity of "magnetic fluid" that produces an acceleration of one unit when applied to a unit mass. The centimetre–gram–second system of units (CGS) was the first coherent metric system, having been developed in the 1860s and promoted by Maxwell and Thomson. In 1874, this system was formally promoted by the British Association for the Advancement of Science (BAAS). The system's characteristics are that density

2773-402: The prefix myria- , derived from the Greek word μύριοι ( mýrioi ), was used as a multiplier for 10 000 . When applying prefixes to derived units of area and volume that are expressed in terms of units of length squared or cubed, the square and cube operators are applied to the unit of length including the prefix, as illustrated below. Prefixes are not usually used to indicate multiples of

2832-520: The prefix for 9 (as mentioned) and the prefixes from 1 to 4 (meth-, eth-, prop-, and but-), which are not derived from words for numbers. These prefixes were invented by the IUPAC, deriving them from the pre-existing names for several compounds that it was intended to preserve in the new system: methane (via methyl , which is in turn from the Greek word for wine), ethane (from ethyl coined by Justus von Liebig in 1834), propane (from propionic , which

2891-405: The prefixes from words with the same spellings (such as duo- and duo ). Several technical numerical prefixes are not derived from words for numbers. ( mega- is not derived from a number word, for example.) Similarly, some are only derived from words for numbers inasmuch as they are word play . ( Peta- is word play on penta- , for example. See its etymology for details.) The root language of

2950-483: The running, swimming and cycling endurance event of the same name) that include the shooting, swimming and running elements as described above, but not the riding. These tend to be held during one day during the winter months when weather conditions are less favourable for the equestrian element. Numerical prefix In many European languages there are two principal systems, taken from Latin and Greek , each with several subsystems; in addition, Sanskrit occupies

3009-460: The standard metre artefact from 1889 was retired. Today, the International system of units consists of 7 base units and innumerable coherent derived units including 22 with special names. The last new derived unit, the katal for catalytic activity, was added in 1999. All the base units except the second are now defined in terms of exact and invariant constants of physics or mathematics, barring those parts of their definitions which are dependent on

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3068-406: The summer months. It is recommended that one skill and one endurance phase is completed on each day. For example, shooting and swimming will be on the first day, riding and running on the second. The competitions are organized using many volunteers and a few paid professionals. The United States Pony Clubs is a non-profit organization, and the competitions are often hosted and subsidized by sponsors of

3127-411: The unit metre and time has the unit second, and speed has the derived unit metre per second. Density, or mass per unit volume, has the unit kilogram per cubic metre. A characteristic feature of metric systems is their reliance upon multiples of 10. For example, the base unit of length is the metre, and distances much longer or much shorter than 1 metre are measured in units that are powers of 10 times

3186-454: The unit. Thus the kilogram and kilometre are a thousand grams and metres respectively, and a milligram and millimetre are one thousandth of a gram and metre respectively. These relations can be written symbolically as: The decimalised system is based on the metre , which had been introduced in France in the 1790s . The historical development of these systems culminated in

3245-644: The world. The French Revolution (1789–99) enabled France to reform its many outdated systems of various local weights and measures. In 1790, Charles Maurice de Talleyrand-Périgord proposed a new system based on natural units to the French National Assembly , aiming for global adoption. With the United Kingdom not responding to a request to collaborate in the development of the system, the French Academy of Sciences established

3304-435: Was added in 1999. The base units used in a measurement system must be realisable . Each of the definitions of the base units in the SI is accompanied by a defined mise en pratique [practical realisation] that describes in detail at least one way in which the base unit can be measured. Where possible, definitions of the base units were developed so that any laboratory equipped with proper instruments would be able to realise

3363-543: Was remedied at the 1893 International Electrical Congress held in Chicago by defining the "international" ampere and ohm using definitions based on the metre , kilogram and second , in the International System of Electrical and Magnetic Units . During the same period in which the CGS system was being extended to include electromagnetism, other systems were developed, distinguished by their choice of coherent base unit, including

3422-530: Was used both in France and in the Soviet Union . Gravitational metric systems use the kilogram-force (kilopond) as a base unit of force, with mass measured in a unit known as the hyl , Technische Masseneinheit (TME), mug or metric slug . Although the CGPM passed a resolution in 1901 defining the standard value of acceleration due to gravity to be 980.665 cm/s , gravitational units are not part of

3481-521: Was used until a new definition was introduced in May 2019 . Replicas made in 1879 at the time of the artefact's fabrication and distributed to signatories of the Metre Convention serve as de facto standards of mass in those countries. Additional replicas have been fabricated since as additional countries have joined the convention. The replicas were subject to periodic validation by comparison to

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