The following will emphasize the importance of the units: Try to learn them by heart as they will be referred to in different units of competency. Students need to familiarise themselves with quantities, symbols and units.
(Many symbols are unfortunately Greek letters) You should try to memorise the symbols and units listedīelow. Symbols and base units used in Competency Units Or alternatively, for use with liquids and gases: VOLUME SI unit: cubic metre (m³) 1000 cubic centimetres (cm³) Tables of measures for mass, length, area and volume are set out belowĪREA SI unit: square metre (m²) 100 square millimetres (mm²) Centimetre is a recognised unit of length but centigram is not a recognised unit of mass. * The prefixes `centi' and `deci' are only used with the metre. The Common Prefixes and Units Prefix & Symbol For instance, since the prefix kilo (k) stands for 1000, 1 kilometre (km) equals 1000 metres (m), and any change from metres to kilometres or vice versa simply involves a decimal point or zeros as shown below. This results from the practical system of attaching to unit names (symbols) standard prefixes that stand for some of the powers of 10 such as 0.001 (milli), 1000 (kilo). One of the main reasons for this is the simple compatibility of the metric system with our world-wide numerals and arithmetic based on the 10 digits and their position relative to a decimal point. The metric system, and especially that part of it called the SI (le Systéme International d'Unités or, in plain English, the International System of Units), is by far the simplest and most rational system of units devised. Some content on this page may previously have appeared on Citizendium.Units and formulas Metric system, symbols & units (1998-2008) Energy: The Physics Hypertextbook™. One ton of TNT releases 4.184 GJ on exploding.A small car (about 1200 kg) travelling at 65 miles per hour (105 km/h) has a kinetic energy of 1 megajoule (1 MJ).One gram of gasoline releases about 50 kJ on combustion in air.One "dietary Calorie" (as used in the United States to designate a kilocalorie) is 4186 J (4.186 kJ).A baseball pitched by a fast Major League pitcher has a kinetic energy of approximately 230 J.One calorie (1 1/1000 of a kilocarie of food consumed or metabolic energy expended) equals 4.186 J.The amount of energy one utilizes in lifting a cup of water from the table to one's mouth equals approximately 1 Joule.One kilogram (kg) of mass is equivalent to exactly 89,875,517,873,681,764 joules (according to E= mc 2 with m = 1 kg and speed of light c = 299,792,458 m/s). Those include: erg foot pound watt second watt hour kilowatt hour thermochemical calorie International Table calorie kilocalorie thermochemical Btu therm quad cubic meter natural gas ton of oil equivalent ton of coal equivalent ton of TNT electron volt hartree inverse meter inverse second kelvin kilogram. Whereas the joule is the standard SI unit of energy, many other units of energy, all convertible to joules, are used in particular circumstances. Other units of energy convertible to joules Often, kilojoules (kJ) are used, kJ = 10 3 J. One joule represents a relatively small amount of energy it takes roughly 100,000 J (10 5 J) to heat a cup of water from room temperature to its boiling point under standard conditions. The joule is named for James Prescott Joule (1818 - 1889), who studied the relation between mechanical and heat energy discovered earlier by count Rumford. One calorie of heat is the equivalent of 4.186 J. The joule is also used to measure thermal energy. The amount of energy delivered by a one watt source of power in one second is one Joule. One joule measures the energy released by a electric charge of one coulomb dropping one volt in absolute value of electrical potential. One may also use electric units to define the joule. 'Joule' is variously pronounced 'jool' (rhymes with 'jewel') or 'joul' (rhymes with 'jowl'). It follows that J (joule) is expressed in SI basic units as: The mechanical quantities involved have the SI units: One newton equals a force that produces an acceleration of one meter per second (s) per second on a one kilogram (kg) mass. One joule equals the work done (or energy expended) by a force of one newton (N) acting over a distance of one meter (m). The joule (symbol J) is the SI unit of energy-a measure of the capacity to do work or generate heat.
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