Metric System

Stucture: Names of metric units and blanks to list examples of what is measured with these units.

Intuition: How large is a liter? A meter? A kilogram?

Interesting facts about the metric system.

Activities: Measure some things.

Conversions: Convert your measurement to different units.

Structure: Names of metric units used in computers and electronics and examples of what is measured with these units.

Structure

In at least five boxes, give an example of some object that is measured in these units. (The ones in bold are most important to know for everyday life. The others are provided to help you see the structure of this system.)

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How large are these?

1. A liter is a little bigger than a quart. (1 L = 1.06 qt)
2. A meter is a little bigger than a yard. (1 m = 1.0936 yd)
3. A kilogram is a little bigger than two pounds. (1 kg = 2.2 lb)

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Interesting facts:

1. A liter of water weighs about a kilogram. (For reference, a pint of water weighs about a pound.)
2. A meter was defined as one ten-millionth of the distance from the North Pole to the equator, through Paris. (Does this give you any clue about what country was doing the definition? Not that it matters which line from the pole to the equator is used.)
3. In one nanosecond, light travels about one foot.
4. Regular computer memory takes about 70 nanoseconds to read and write something. Really expensive, really fast computer memory takes about 10 nanoseconds.
5. The other measure of capacity that is often used is cubic centimeters. (Generally, chemists use liters, etc., and physicists use cubic centimeters.) A milliliter is the same as a cubic centimeter.
6. Metric units for time were developed along with the other metric units, but didn't catch on, so no one uses them now.
7. In countries that use the metric system, for temperature, degrees Centigrade (Celsius) is used. It assigns 0 to the freezing point of plain water and 100 to the boiling point of plain water at sea level.
8. I have been told that Mr. Fahrenheit, who developed the Fahrenheit temperature scale, was also using 0 and 100 as his interesting points. His 0 was set to be the freezing point of water that has as much salt in it as the water can dissolve, and 100 was set to be normal body temperature of a human. (Later scientists hypothesize that Mr. Fahrenheit had a chronic disease, so he had a low-grade fever, which made his body temperature as high as 100.) Of course, we don't think of degrees Fahrenheit as a metric system, partly because we have accepted the freezing and boiling points of plain water as the most reasonable end points and also because of Mr. Fahrenheit's mistake about the normal body temperature of a human.
9. Metric units for angles were developed too. They are called grads. One hundred grads is the same as 90 degrees, in our usual angle measure. I don't know of any application that uses grads for angles, but most of our scientific calculators have it as one option for measuring angles (along with degrees and radians.)

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A "hand" is a measurement of length in the English system that is used to measure the height of horses. (Put your hand flat on a table or desk with the fingers and thumb together and measure from the outside of the little finger to the outside of the thumb. A "cubit" is a measurement of length in mentioned in the Bible. (Measure from the point of your elbow to the tip of your longest finger.)

1. Pick a desk. Have at least four people measure the length of the top of that same desk, in "hands". Write down the measurements here. How variable are these?

2. Use the table at the front of the room. Have at least four people measure the length of the table in cubits. Write down the measurements here. How variable are these?

3. Get a meter stick or a tape measure with metric length units marked on it. The numbered units are centimeters. Each centimeter is divided into ten parts, which are millimeters. Pick a book. Have at least four different people measure its height and write down the measurements here, in centimeters. How variable are these?

4. Measure the length of the table in the front of the room in some metric system units. Write your measurement here, making clear what the units are. (Call the units either m, cm, or mm)

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Conversions

Now practice conversions. Recall the method we learned for converting measurements from one unit to another. Write your measurement for the length of the table in the appropriate blank below and then convert it into each of the other units. (Use 1m = 3.2808 ft. All the other conversion factors that are needed are ones you should know.) Show your work on the right. Then check to see if the answer makes sense.

________ millimeters

________ centimeters

________ meters

________ kilometers

________ inches

________ feet

________ yards

________ miles

6. In the metric system, which units seem to be the most convenient way to report the length of a table? ______________ In the American system, which units seem to be the most convenient for reporting the length of a table? _____________

7. Why do you think measurements such as "hands" and "cubits" are not used as much as centimeters, meters, inches, and feet?

8. Why do you think that some people prefer the metric system to the English system when they are converting measurements from one type of units to another? (Like meters to kilometers compared to feet to miles.)

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