THE METRIC SYSTEM

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THE METRIC SYSTEM
SOME DAY, WELL BE TRADING OUR FEET FOR METERS.
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MEASUREMENT NUMBERS ARE OBTAINED BY COUNTING OR
DEFINITION MEASUREMENTS ARE OBTAINED BY
COMPARING THE OBJECT IN QUESTION TO A STANDARD
UNIT NUMBERS ARE EXACT, BUT MEASUREMENTS ARE
INEXACT (HAVE A CERTAIN DEGREE OF
ERROR). MEASUREMENTS CONSIST OF TWO PARTS A
NUMERIC VALUE AND A UNIT.
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THE SO CALLED ENGLISH SYSTEM OF MEASUREMENTS IS
STILL USED IN A FEW COUNTRIES, INCLUDING THE
U.S. IT IS A SYSTEM THAT GOES BACK TO ROMAN
TIMES, AND IT HAS BEEN CHANGED SEVERAL TIMES.
FOR EXAMPLE, THE ROMAN FOOT WAS SLIGHTLY LESS
THAN 12 INCHES, AND THE ANGLO-SAXON FOOT WAS
SLIGHTLY MORE.
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THE FOOT AS WE KNOW IT WAS STANDARDIZED UNDER THE
REIGN OF HENRY THE 1 (1100 1135). THE ROMAN
MILE HAD BEEN 5000 FEET, BUT THIS WAS CHANGED TO
5280 FEET TO MAKE IT AN EVEN NUMBER OF
FURLONGS. THE SYSTEMS OF MEASURING VOLUME AND
WEIGHT ARE EQUALLY CRAZY.
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WITH INTERNATIONAL TRADE, MOST OF THE WORLD HAS
GONE TO THE SI OR METRIC SYSTEM.
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(CNN) -- NASA lost a 125 million Mars orbiter on
September 23, 1999 because a Lockheed Martin
engineering team used English units of
measurement while the agency's team used the more
conventional metric system for a key spacecraft
operation, according to a review finding released
Thursday.
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THE METRIC SYSTEM IS BASED ON THREE DEFINED
UNITS. m the meter for length kg the
kilogram for mass s the second for time ALL
THE OTHER UNITS ARE DERIVED FROM THESE THREE. BY
COMPARISON 1 m 1.094 yard 1 kg 2.205
lb 1 s 1 s
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WE CAN COMBIND THE KILOGRAM, THE METER, AND THE
SECOND TO MAKE MORE UNITS. AREA LENGTH X
LENGTH m x m m2 VOLUME L X L X L m x m x
m m3 1 m3 1,000 liters The liter is the
unit we will use for volume. 1 liter 1.05669
quarts 1.06 quarts
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THE ORIGINAL METRIC SYSTEM WAS STARTED IN FRANCE
IN 1670. THE SYSTEM, AS WE KNOW IT, WAS PUT IN
PLACE IN 1960, AND IS KNOWN AS THE INTERNATIONAL
SYSTEM OF MEASUREMENT, OR "Système International
IN FRENCH OR SI.
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OUR MORE COMMON UNITS OF MEASURE MASS gram,
g 454 grams 1 lb 1 kilogram, kg
1000 g 1 milligram 0.001 g VOLUME liter,
l 1 l 1.06 quarts 1 milliliter, ml 0.001
l LENGTH meter, m 1 meter 1.09 yard 1 cm
0.01 m 2.54 cm 1 inch 1 mm 0.001 m
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THE SI SYSTEM USES PREFIXES TO CONVERT THE BASE
UNITS TO UNITS THAT ARE MORE USEABLE FOR OUR
GIVEN APPLICATIONS.
Prefix Abbreviation Meaning
Mega M 106
Kilo K 103
Centi c 10-2
Milli m 10-3
Micro ?? 10-6
Nano n 10-9
Pico p 10-12
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SOME COMPARISONS LENGTH A DIME IS 1 mm
THICK A QUARTER IS 2.5 cm DIAMETER AV.
HEIGTH OF ADULT MALE 1.8 m MASS A NICKEL IS 5
g A 120 lb PERSON HAS A MASS OF 55
kg VOLUME A 12 oz SODA HAS A VOLUME OF 360
ml
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ANOTHER IMPORTANT MEASUREMENT IS
TEMPERATURE. TEMPERATURE IS A MEASURE OF THE
AVERAGE KINETIC ENERGY. THE HIGHER THE
TEMPERATURE, THE FASTER THE PARTICLES THAT MAKE
UP THE OBJECT ARE VIBRATING (SOLID) OR MOVING
(LIQUID OR GAS). THERE ARE THREE TEMPERATURE
SCALES THAT ARE USED FAHRENHEIT, CELCIUS, AND
KELVIN.
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THESE SCALES DIFFER BY THE TEMPERATURES SELECTED
FOR THE REFERENCE POINTS. THEY ALL USE THE SAME
THREE REFERENCE POINTS - THE BOILING POINT OF
WATER - THE FREEZING POINT OF WATER - ABSOLUTE
ZERO THE EXTERNAL PRESSURE IS 1 ATMOSPHERE (760
MM Hg) FOR THE BOILING POING AND THE FREEZING
POINT.
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oC 5/9 (oF - 32) Between the freezing point of
water and the boiling point of water, there are
100 degrees on the Celcius scale and 180 degrees
on the Farenheit scale. The 5/9 corrects for the
difference in the size of the degree. The Celcius
scale sets the freezing point of water at 0o, and
the Farenheit scale sets the freezing point at
32o. oF 9/5 oC 32
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THE KELVIN SCALE IS USED FOR MOST SCIENTIFIC
CALCULATIONS AS TEMPERATURE IN THAT SCALE IS
DIRECTLY PROPORTIONAL TO AVERAGE KINETIC
ENERGY. oK oC 273o
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ANY MEASUREMENT HAS TWO PARTS A NUMBER AND A
UNIT. 12 grams number units WE REPORT
A MEASUREMENT BY RECORDING ALL THE CERTAIN DIGITS
PLUS THE FIRST UNCERTAIN DIGIT. THESE ARE CALLED
SIGNIFICANT FIGURES.
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WHEN YOU ARE DOING AN EXPERIMENT, YOU SHOULD
RECORD YOUR RESULTS TO THE APROPRIATE NUMBER OF
SIGNIFICANT FIGURES THIS WAY, THE UNCERTAINTY
IN MEASUREMENT WILL BE KNOWN. FOR EXAMPLE,
RATHER THAN WRITING 25 ml IF YOUR MEASUREMENT
IS ACCURATE TO THE NEAREST 0.01 ml, YOU WOULD
WRITE 25.00 ml
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A COUPLE OF TERMS YOU WILL HERE IN REFERENCE TO
MEASUREMENTS ARE ACCURACY REFERS TO THE
AGREEMENT OF A PARTICULAR VALUE WITH THE TRUE
VALUE. PRECISION REFERS TO THE DEGREE OF
AGREEMENT AMONG SEVERAL VALUES.
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http//www.chem.sc.edu/faculty/morgan/resources/si
gfigs/index.html THIS IS A TUTORIAL ON THE USE
OF SIGNIFICANT FIGURES. WORK THE FIRST 10 SAMPLE
PROBLEMS.
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It's so hard when I have to, and so easy when I
want to. - Annie Gottlier -