Metric Units
A.K.A. (SI) Units
We will study both the American and the Metric
systems for the following physical quantities.
Length,
Weight, and
(fluid) Volume
DID YOU KNOW
It’s a metric world
The united states is the only
western country not presently
using the metric system as its
primary system of measurement.
The only other countries in the
world not using metric system as
their primary system of
measurement are Yemen, Brunei,
and a few small islands; see
Fig. 8.15.
DID YOU KNOW
Lost in space
In September 1999, the United
States lost the Mars Climate
Orbiter as it approached Mars. The
loss of the $125 million spacecraft
was due to scientists confusing
English units and metric units.
The missing Mars Climate Orbiter
Length
American standard
Metric standard
1 mile = 1760 yards
= (5280 feet)
1 yard = 3 feet
1 foot = 12 inches
1 mil = 1/1,000 inch
1 kilometer = 1000 meters
1 meter = 10 decimeters
1 decimeter = 10 centimeters
( 1 meter = 100 centimeters)
1 centimeter = 10 millimeters
Conversion:
1 inch is defined to be exactly 2.54 cm in July, 1959.
(before this, the UK inch measures 2.53998 cm, while the US
inch was 2.540005 cm)
Do you know?
The word “mile” comes from the Latin mille passum,
literally “thousand paces,” a unit introduced to Britain by
the Roman occupation (57 BCE–450 CE).
Each Roman pace is equal to 5 Roman feet, hence
there were 5000 Roman feet in a Roman mile.
But why does the British mile have grown to 5280 feet?
The British has another unit “furlong” for measuring length
and area. A furlong has 660 ft and it does not divide into 5000
evenly. So Elisabeth I defined a mile to be 8 furlongs and
hence 5280 feet.
A furlong is the distance a team of oxen could plow without
needing a rest.
Historical Note
The kilometer was first
defined by the French
Academy of Science in 1791
as the romantic one tenthousandth of the length of
the meridian through Paris
from the North pole to the
equator.
Weight
American Standard
Metric Standard
1 ton = 2000 pounds
1 pound = 16 ounces
1 (metric) tonne = 1000 kilograms
1 kilogram = 1000 grams
1 gram = 1000 milligrams
Conversion:
1 pound = 0.453 592 37 kilograms
hence
1 kilogram  2.2 pounds
by the way …
The abbreviation for the
pound, lb, comes from
the Latin libra, meaning
“scales”.
A dollar bill weighs about 1 gram,
a dime weighs about 2 grams,
and a quarter 5 grams.
by the way …
Carat
is a unit of mass used for diamonds and other precious stones.
The word carat comes from the Greek keration, a carob bean;
the seed of a Mediterranean evergreen tree.
Traditionally the carat was equal
to 4 grains. The definition of the
grain differed from one country
to another, but typically it was
about 50 milligrams and thus the
carat was about 200 milligrams.
In the U. S. and Britain, the diamond carat was formerly defined
by law to be 3.2 troy grains, which is about 207 milligrams.
Jewelers everywhere now use a metric carat defined in 1907 to
be exactly 200 milligrams or 0.2 gram.
Volume for liquid
American Standard
Metric Standard
1 gallon = 4 quarts
1 quart = 2 pints
1 pint = 16 fluid ounces
1 liter = 1000 milliliters
1 milliliter = 1 c.c.
(also 1 pint = 2 cups
1 cup = 16 Tablespoons
1 TBS = 3 teaspoons
)
Conversion:
1 gallon = 3.785 411 784 liters
 3.8 liters
1 gallon = 231 cubic inches
MR. GALLON IS A VISUAL AID TO REMEMBER THE
AMOUNTS IN EACH MEASUREMENT.
Do you know?
Fact: one c.c. of water weighs 1 gram at standard temperature.
How much does one gallon of water weigh?
Answer: approx. 8.34 lb.
How much does one gallon of gasoline weigh?
Answer: varies between 5.8 to 6.5
depending on its type
Area
American Standard
1 square mile = 640 acres
1 acre = 43560 square feet
Historical Note
An acre is originally defined
as the amount of land a pair
of oxen could plow in a day.
F.Y.I.
A football field (including end zones)
measures 57600 sq feet, hence it is equal to
1.322 acres, or approximately 1 and ½ acres.
Temperature
American standard
Metric Standard
Fahrenheit
32 ºF = freezing
212 ºF = boiling
Celsius
0 ºC = freezing
100 ºC = boiling
(for pure water)
(for pure water)
Conversion:
F = 1.8 × C + 32
C = (F – 32)/1.8