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# What is the difference between fundamental and derived quantities?

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The metric system (SI) defines seven fundamental quantities that cannot be further broken down, from which all other derived quantities come. The meter is the fundamental quantity for length. Area uses the derived quantity of square meters and volume uses cubic meters.

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When measuring very small or very large units, use of the fundamental unit often becomes cumbersome. Measuring the width of a human hair using the meter requires a decimal point and several zeros. The SI system handles this prefixes that describe multiplying the base unit by a power of ten. Measuring the hair in nanometers (0.000000001 meter) is more appropriate.

Units such as the day, hour and astronomical unit, are not officially a part of the metric system, but they are often used in science. These units are also possible to derive from the SI fundamental quantities. For example, a day is 86,400 seconds, according to HowStuffWorks.

Some derived units have special names. For example, the metric system also uses the liter to measure volume. One liter is 1000 cubic centimeters. The Newton, for measuring force, is the product of acceleration (meters per second squared) and mass (kilogram) or kilogram meter per second squared. Many of the special names given to the derived units honor the work of scientists in the area the unit represents.

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## Related Questions

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The metric system is advantageous because it doesn't require conversions or use fractions. There are also fewer units in the metric system, and it uses simpler prefixes. The main disadvantage is having to teach someone who's used to using imperial units how to use the metric system.

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The prefixes used within the metric system serve to designate a multiple or subdivision of a unit. The most common prefixes include: mega-, kilo-, centi-, milli- and nano-. All prefixes designate a power of 10.

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Depending on the specific conversion a person may require, 1 milligram can equal 1000 micrograms, 0.001 gram, or 0.1 centigrams in the metric system. However, 1 milligram can also be converted to different Imperial measurements like ounces and drams.