S.I. units  #1 An Introduction
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welcome to speed physics introducing the SI family of Units there are seven of them in all the meter symbol lowercase M the kilogram symbol lowercase kg second symbol lowercase s the ampere symbol capital a the Kelvin symbol capital K the mole symbol mole in lower case the Candela symbol lowercase C D so what do we know about s re Lauper’s s is an acronym which is really an abbreviation or shorthand for a word or group of words it often takes the form of a jumble of letters and sometimes numbers with each letter represented a word though this is not set in stone examples are DVD digital video disc 3d three-dimensional HST Hubble Space Telescope get my drift so what does si stand for systm international unity which means the International System of Units as you might have guessed the system Internacional is French why because the French started the race to give the world a consistent set of units it goes back to the 1790s so king louis xvi the french government and the academy of sciences got together to commissioned a new unified system of measures the system was administered by a small group of scientists and mathematicians headed by antoine laurent lavoisier you might have heard of La YCA sometimes called the father of chemistry he discovered oxygen and laid the foundation of good chemistry practice by carefully weigh in reactants and products the group also included the eminent mathematicians Laplace and Legendre plus a host of many interested scientists and mathematicians before that time in Europe all measurement was in a mess and especially infants there were so many different units for length and weight and popular units Varian value across the country so if you bought a lever of potatoes in Paris you might be shortchanged if you bought the same amount in Calais the same was true of the own a unit of length so buying seven own of best sell had its risks anyway the French Revolution happened and with it a particularly bloody episode the reign of terror unfortunately king louis xvi was guillotine in 1793 and Lavoisier soon after in 1794 by 1799 both the metre and the kilogram had been defined as time went by and the news of the unit system spread other countries got involved eventually an international body was set up the system Antonis TL do we betta anyway in the 19th century things gathered apace contributions were made by many famous scientists among them carl friedrich gauss James Clark Maxwell and William Thompson later Lord Kelvin however as time went by centimeter and the gram were deemed too small for serious scientific work so was replaced by the MKS system based on the metre the kilogram and the second later amendments added to the basic three units to our present a tally of seven units and this is what we call the SI system these seven units are displayed here from the perspective of the quantity they measure quantity length quantity symbol L unit meter unit symbol M quantity mass quantity symbol M unit kilogram unit symbol kg quantity time quantity symbol T unit second unit symbol s quantity electric current quantity symbol capital I unit unpair unit symbol capital a quantity thermodynamic temperature quantity symbol capital t unit kelvin unit symbol capital K quantity amount of substance quantity symbol n unit mole unit symbol mall quantity luminous intensity quantity symbol capital I subscript capital V unit Candela unit symbol CD don’t worry if this seems too much to swallowing one go each of these units will have its own video remember if you subscribe to the channel you will be among the first to view any release any teacher will tell you being successful at physics is like building the pyramid if you want to reach the topmost levels you must build on firm foundations and that means knowing your units subscribe to speed physics buckle up and get in strike your highway to the easy and the not so easy lots of physics

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