Metric System

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Metric System

• Simple Consistent

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Measurement up to 1790not a pretty picture!

• measurement requires a recognizable standard for
  all
• but
• until 1790s
• every region had
• own standards

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Standards

• standard something used as comparison
• for measuring
• standard must
• be available for everyone to use
• be something in nature that is same everywhere
• never vary

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1585 Simon Stevin

• introduced use of decimals in Europe
• to allow for parts of a whole
• predicted universal introduction of decimal
  coinage, measures and weights

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1670 Gabriel Mouton

• 1st to propose decimal system of measurement
  based on size of earth
• Earth-based standard 1?of longitude

Earth is standard available to everyone! What
an idea!
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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)

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1790 French Academy of Sciences created the
metric system

• 3 Requirements

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1Basic Standard Earth

• unit of length is portion of Earth's
  circumference

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2Internal Consistency

• units for capacity (volume/space) and mass
  related to unit of length

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3Ease of Use - Calculations

• larger and smaller units created by multiplying
  or dividing basic units by factors of 10

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Fundamental (Base) Units

• based on object/event in nature
• SI system has 7 fundamental units
• probably already know 4 of them
• any guesses as to which ones you know?

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7 Fundamental Quantities of SI
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Derived Units

• combinations of fundamental units
• examples
• speed (meters/second)
• area (length x width)
• volume (length x width x height)
• density (mass / volume)

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Ease of Use - Names

• larger smaller multiples of same unit named by
  
• series of prefixes relating to base
  unit

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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)

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(No Transcript)
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Prefixes in the SI System
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Prefixes

• used for all 7 fundamental units!
• kilometer
• milliliter
• centigram
• microsecond
• nanokelvin

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1790 - Jefferson

• proposed decimal-based measurement system for US
• cons
• no prefixes
• too many
• names

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1792 U.S. Mint

• produced worlds 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

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What is a 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
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• liter based on meter, which is based on Earth

10 cm
10 cm
10 cm
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defined as mass of 1 liter water at 4C Why
water?
kilogram is based on liter, which is based on
meter, which is based on Earth
10 cm
10 cm
10 cm
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What is a second?
originally defined as 1/86,400th of average solar
day
defined now in terms of electron transitions in
Cs-133
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What is a Kelvin?
Kelvin is defined in terms of water absolute
zero
0 K Absolute zero bp of H2O 100?C 373 K mp
of H2O 0?C 273 K
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What is a mole?

• amount any substance that has as many particles
  as atoms found in 0.012 kg of carbon-12

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prototype kilogram stored in vault in France