Metric System
SI Units
Scientists use a different method of recording data than Americans are used to. Americans are used to weights being measured in pounds and ounces, lengths measured in inches, feet and miles and volumes measured in cups, pints, quarts and gallons. Because there are so many units, scientists have developed standards in which they use to take measurements.
The System Internationale Units, or SI Units, are the standards set by the scientific community. The following table lists the standards:
Scientists use a different method of recording data than Americans are used to. Americans are used to weights being measured in pounds and ounces, lengths measured in inches, feet and miles and volumes measured in cups, pints, quarts and gallons. Because there are so many units, scientists have developed standards in which they use to take measurements.
The System Internationale Units, or SI Units, are the standards set by the scientific community. The following table lists the standards:
Measurement
Length Mass Temperature Time Volume Computer Information |
Metric Base Unit
meter (m) gram (g) Kelvin (K) second (s) Liter (L) bytes |
Metric System
The meter is approximately 39 inches long. This length is really good for measuring the height of a person, or the distance across a room. However, the meter is not an effective way to measure the distances between New York and Los Angeles. It could be done, but picking up and moving the meter stick that many times could take you months! Similarly, the width of the table top is not best measured using the meter. A smaller unit would better represent the width.
To rectify this, the metric system allows for a prefix, placed in front of the base unit, to make the unit either bigger or smaller by a factor of 10. The prefixes will depend upon whether the base needs to be made smaller or bigger. The metric system prefixes look like this:
The meter is approximately 39 inches long. This length is really good for measuring the height of a person, or the distance across a room. However, the meter is not an effective way to measure the distances between New York and Los Angeles. It could be done, but picking up and moving the meter stick that many times could take you months! Similarly, the width of the table top is not best measured using the meter. A smaller unit would better represent the width.
To rectify this, the metric system allows for a prefix, placed in front of the base unit, to make the unit either bigger or smaller by a factor of 10. The prefixes will depend upon whether the base needs to be made smaller or bigger. The metric system prefixes look like this:
Prefix
Tera Giga Mega kilo hecto deka base deci centi milli micro nano pico femto |
Symbol
T G M k h dk d c m n
p f |
Multiply/Factor of base
1,000,000,000,000 (1 trillion times) 1,000,000,000 (1 billion) 1,000,000 1,000 100 10 1 1/10 1/100 1/1000 1/1,000,000 1/1,000,000,000 (1 billionth) 1/1,000,000,000,000 (1 trilllionth) 1/1,000,000,000,000,000 (1 quadrillionth) |
The metric prefixes are typically arranged like this, with b being the base.
As you can see from the two diagrams, the metric system allows for the base to be changed by a factor of ten. For instance if you measure a distance in kilometers (km), the length of 1 measure is 1000 meters. Imagine putting 1000 meter sticks end to end and then glueing them altogether. When you pick it up, you have one kilometer stick. Or if you measure a length in millimeters (mm), then the length of measure used is 1/1000 of a meter. Imagine taking one of those meter sticks and cutting it into 1000 equal pieces. In this case, each one of the sticks would now be a millimeter stick.
The metric system is a base 10 system, which means that to change from one prefix to another, it is necessary to either multiply or divide by factors of 10 (i.e., 10, 100, 1000, 1/10, 1/100). Because of the factors of 10, to move from one prefix to another, it is really only necessary to move the decimal point (when you divide by 100, you move the decimal 2 places to the left).
Suppose you knew of a distance that was 200 km, and you wanted to know how far that distance would be in meters. Meters is the base, which is 3 spots to the right of kilo-, therefore, you would need to move the decimal three spaces to the right to transfer the number into meters.
The metric system is a base 10 system, which means that to change from one prefix to another, it is necessary to either multiply or divide by factors of 10 (i.e., 10, 100, 1000, 1/10, 1/100). Because of the factors of 10, to move from one prefix to another, it is really only necessary to move the decimal point (when you divide by 100, you move the decimal 2 places to the left).
Suppose you knew of a distance that was 200 km, and you wanted to know how far that distance would be in meters. Meters is the base, which is 3 spots to the right of kilo-, therefore, you would need to move the decimal three spaces to the right to transfer the number into meters.
Now you try it. Suppose something massed 0.00045 Mg and you wanted to know the weight in ng. How many times would you need to move the decimal? In which direction? And what would be the mass in ng?
Answer: 15 times to the right, resulting in a value of 450000000000 ng.
Answer: 15 times to the right, resulting in a value of 450000000000 ng.