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Metric System

Simple & Consistent. Metric System. Measurement up to 1790: not a pretty picture!. measurement requires a recognizable standard for all but… until 1790 ’ s every region had own standards. Standards. “ standard: something used as comparison for measuring ”

brett-burns
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Metric System

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  1. Simple & Consistent Metric System

  2. Measurement up to 1790:not a pretty picture! measurement requires a recognizable standardfor all but… until 1790’s every region had own standards

  3. Standards • “standard: something used as comparison for measuring” • standard must: • be available for everyone to check measurements • be something in nature that issame everywhere • never vary

  4. 1585 – Simon Stevin • introduced use of decimals in Europe • allows for parts of a whole • predicted universal introduction of decimal coinage, measures and weights

  5. 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!

  6. 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)

  7. 3 Requirements 1790 – French Academy of Sciences created the metric system

  8. # 1Basic Standard = Earth • unit of length is portion of Earth's circumference

  9. #2Internal Consistency • units for capacity (volume/space) and mass related to unit of length

  10. #3Ease of Use - Calculations • larger and smaller units created by multiplying or dividing basic units by factors of 10

  11. 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?

  12. QUANTITY UNIT ABBREVIATION length meter m mass kilogram kg time second s temperature kelvin K amount of substance mole mol luminous intensity candela cd electric current ampere A 7 Fundamental Quantities of SI

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

  14. Ease of Use - Names larger & smaller multiples of same unit named by series of prefixesrelating to base unit

  15. 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)

  16. Prefix Symbol Value Power Use giga G 1,000,000,000 109 gigabyte mega M 1,000,000 106 megamillion kilo k 1,000 103 kilometer deci d 0.1 10-1 decimeter centi c 0.01 10-2 centimeter milli m 0.001 10-3 millimeter micro  0.000001 10-6 micrometer nano n 0.000000001 10-9 nanometer Prefixes in the SI System

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

  18. 1790 - Jefferson • proposed decimal-based measurement system for US cons: no prefixes &too many names

  19. 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

  20. 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

  21. defined as cube measuring • 10 centimeters on each • side (1000 cm3) What is a Liter? • liter based on meter, which is based on Earth 10 cm 10 cm 10 cm

  22. What is a kilogram? defined as mass of 1 liter water at 4°C Why water? kilogram is based on liter, which is based on meter, which is based on Earth 10 cm 10 cm 10 cm

  23. What is a second? originally defined as 1/86,400th of average solar day defined now in terms of electron transitions in Cs-133

  24. 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

  25. What is a mole? amount any substance that has as many particles as # atoms found in 0.012 kg of carbon-12

  26. prototype kilogramstored in vault in France

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