Metric UnitsA.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 KNOWLost 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

LengthAmerican standard

1 mile = 1760 yards = (5280 feet)1 yard = 3 feet1 foot = 12 inches1 mil = 1/1,000 inch

Metric standard

1 kilometer = 1000 meters1 meter = 10 decimeters1 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 ten-thousandth of the length of the meridian through Paris from the North pole to the equator.

Weight

American Standard

1 ton = 2000 pounds1 pound = 16 ounces

Metric Standard

1 (metric) tonne = 1000 kilograms1 kilogram = 1000 grams1 gram = 1000 milligrams

Conversion:1 pound = 0.453 592 37 kilogramshence1 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 liquidAmerican Standard

1 gallon = 4 quarts1 quart = 2 pints1 pint = 16 fluid ounces

(also 1 pint = 2 cups 1 cup = 16 Tablespoons 1 TBS = 3 teaspoons )

Metric Standard

1 liter = 1000 milliliters1 milliliter = 1 c.c.

Conversion:1 gallon = 3.785 411 784 liters 3.8 liters1 gallon = 231 cubic inches

MR. GALLON IS A VISUAL AID TO REMEMBER THE AMOUNTS IN EACH MEASUREMENT.

Do you know?

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

Fact: one c.c. of water weighs 1 gram at standard temperature.

AreaAmerican Standard

1 square mile = 640 acres1 acre = 43560 square feet

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.

Historical NoteAn acre is originally defined as the amount of land a pair of oxen could plow in a day.

Temperature

American standard

Fahrenheit32 ºF = freezing212 ºF = boiling

(for pure water)

Metric Standard

Celsius0 ºC = freezing100 ºC = boiling

(for pure water)

Conversion:

F = 1.8 × C + 32 C = (F – 32)/1.8