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 yard
1 kg = 2.205 lb
1 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 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
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 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
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.
number
12 grams
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 -