The Metric System A Review of Measurement & The Metric System.
Metric System
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Transcript of Metric System
Metric System Simple &
Consistent
Measurement up to 1790:not a pretty picture!
measurement requires a recognizable standardstandard for all but… until 1790’s every region had own standards
Standards• “standard: something used as
comparison for measuring”
– standard must:•be available for everyoneavailable for everyone to check measurements
•be something in nature that be something in nature that isis same same everywhereeverywhere
•never varynever vary
1585 – Simon Stevin• introduced use of decimals in
Europe– allows for parts of a whole
•predicted universal introduction of decimal coinage, measures and weights
1670 – Gabriel Mouton•1st to propose decimal system of
measurement based on size of based on size of earthearth
•Earth-based standard: 1of longitude Earth is standard Earth is standard
available to everyone! available to everyone! What an idea!What an idea!
Systeme International (SI)
• based on metric system• invented in 1790*
– originally, earth-based standards– volume & mass linked to length– larger & smaller multiples of each unit
related by powers of 10
*updated every few years (major changes in 1960 and 1991)
1790 – French Academy of Sciences createdcreated the metric
system
3 Requirements
# 1Basic Standard = Earth
•unit of length is portion of Earth's circumference
#2Internal Consistency
•units for capacity (volume/space) and mass relatedrelated to unit of length
#3Ease of Use - Calculations
•larger and smaller units created by multiplying or dividing multiplying or dividing basic units by basic units by factors of 10factors of 10
Fundamental (Base) Units
•based on object/event in nature
•SI system has 77 fundamental units
•probably already know 4 of them• any guesses as to which ones you know?
ABBREVIATIONUNITQUANTITY
mmeterlength
kgkilogrammass
Kkelvintemperature
ssecondtime
cdcdcandelacandelaluminous intensityluminous intensity
AAampereampereelectric currentelectric current
molmolmolemoleamount of amount of substancesubstance
7 Fundamental Quantities of SI7 Fundamental Quantities of SI
Derived Units
• combinations of fundamental units
• examples:– speedspeed (meters/second)– areaarea (length x width)– volumevolume (length x width x height)– densitydensity (mass / volume)
Ease of Use - Names
larger & smaller multiples of same unit named by
series of prefixesprefixes relating to base unit
smaller units•1/10 of meter = decimeter (dm)•1/100 of meter = centimeter (cm)•1/1000 of meter = millimeter (mm)
larger units•10 meters = dekameter (dam)•100 meters = hectometer (hm)•1000 meters = kilometer (km)
UsePowerValueSymbolPrefix
gigabyte1091,000,000,000Ggiga
megamillion1061,000,000Mmega
kilometerkilometer1010331,0001,000kkkilokilo
decimeter10-10.1ddeci
centimetercentimeter1010-2-20.010.01cccenticenti
millimetermillimeter1010-3-30.0010.001mmmillimilli
micrometer10-60.000001micro
nanometer10-90.000000001nnano
Prefixes in the SI SystemPrefixes in the SI System
Prefixes
•used for all 7 fundamental units!–kilometermeter–milliliterliter–centigramgram–microsecondsecond–nanokelvinkelvin
1790 - Jefferson• proposed decimal-based measurement
system for US
cons:
no prefixes
& too many
names
1792 – U.S. Mint
• produced world’s first decimal currency (one dollar = 100 cents)
• 100 cents in dollar• 4 quarters in dollar• 10 dimes in dollar• 20 nickels in dollar
can see how this can be confusing:-names not related to each other -no consistency with parts of dollar
What is a What is a meter?meter?
1790: 1//10,000,000 th of distance from North pole to equator
1983: distance light travels in vacuum in 1//299,792,458 th of second
What is a LiterLiter?• defined as cube
measuring 10 centimeters on each
side (1000 cm3)
10 cm
10 c
m
10 cm
•liter based on meter, which is based on Earth
What is a kilogramkilogram?
10 cm
10 c
m
10 cm
defined as mass of 1 liter water at 4°C
Why waterWhy water?
kilogram is based on liter, which is based on meter, which is based on Earth
What is a secondsecond?originally defined as 1/86,400th of average solar day
defined now in terms of electron transitions in Cs-133
What is a KelvinKelvin?
Kelvin is defined in terms of water & absolute zero
0 K = Absolute zero0 K = Absolute zero
bp of Hbp of H22O = 100C = 373 O = 100C = 373 KKmp of Hmp of H22O = 0C = 273 O = 0C = 273 KK
What is a mole mole?
amount any substance that has as many particles as # atoms found in 0.012 kg of carbon-12
prototype kilogramkilogram stored in vault in France