THE METRIC SYSTEM

SOME DAY, WE’LL BE TRADING OUR FEET FOR METERS.

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.

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.

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.

WITH INTERNATIONAL TRADE, MOST OF THE WORLD HAS GONE TO THE SI OR METRIC SYSTEM.

(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.

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 yard1 kg = 2.205 lb1 s = 1 s

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

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.

OUR MORE COMMON UNITS OF MEASURE:

MASS: gram, g 454 grams = 1 lb1 kilogram, kg = 1000 g1 milligram = 0.001 g

VOLUME: liter, l 1 l = 1.06 quarts1 milliliter, ml = 0.001 l

LENGTH:meter, m 1 meter = 1.09 yard1 cm = 0.01 m 2.54 cm = 1 inch1 mm = 0.001 m

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

SOME COMPARISONS

LENGTH: A DIME IS 1 mm THICKA QUARTER IS 2.5 cm DIAMETERAV. HEIGTH OF ADULT MALE 1.8

m

MASS: A NICKEL IS 5 gA 120 lb PERSON HAS A MASS OF 55 kg

VOLUME: A 12 oz SODA HAS A VOLUME OF 360 ml

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.

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.

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

THE KELVIN SCALE IS USED FOR MOST SCIENTIFIC CALCULATIONS AS TEMPERATURE IN THAT SCALE IS DIRECTLY PROPORTIONAL TO AVERAGE KINETIC ENERGY.

oK = oC + 273o

ANY MEASUREMENT HAS TWO PARTS – A NUMBER AND A UNIT.

12 gramsnumber units

WE REPORT A MEASUREMENT BY RECORDING ALL THE CERTAIN DIGITS PLUS THE FIRST UNCERTAIN DIGIT.

THESE ARE CALLED SIGNIFICANT FIGURES.

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

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.

http://www.chem.sc.edu/faculty/morgan/resources/sigfigs/index.html

THIS IS A TUTORIAL ON THE USE OF SIGNIFICANT FIGURES. WORK THE FIRST 10 SAMPLE PROBLEMS.

It's so hard when I have to, and so easy when I want to.

- Annie Gottlier -