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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.

## Related Questions

• A:

A millibar is part of the metric system and is a unit of pressure. It is abbreviated by mbar or mb and is derived from the bar.

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• A:

After converting to the metric system, 187 pounds is equal to 84.82 kilograms. The formula to convert between pounds and kilograms divides the number of pounds by 2.2. Dividing 187 pounds by 2.2 yields the answer 84.82 kilograms.

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The equivalent of 1 inch in the metric system is 2.54 centimeters, so to convert 32 inches to centimeters solve the equation x centimeters = (32 inches) (2.54 centimeters / 1 inch). Since inches are cancelled out, the new equation is x centimeters = (32) (2.54) centimeters.