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# SI Base Units

## Seven units that all other metric units are based on.

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Why hasn't the US adopted the metric system?

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The SI base units, used in the metric system, are the following:

Length  - meter (m)

Mass – kilogram (kg)s

Kinetic Energy – joules (J)

Temperature – kelvin (K)

Time – Second (s)

Amount of a Substance – mole (mol)

Electric current – ampere (A)

Luminous Intensity – candela (cd)

The SI units have been adopted in almost every country around the world so it is important that you too understand how to use them. But if the metric system is one of the most common measuring systems used throughout the world, why hasn’t the United States adopted it? Officially, the United States actually HAS adopted it partly but we don’t use it in our everyday life. The reason is because once a course is chosen, it is difficult to convince people to switch. Until the 1990s the United States had very little incentive to do so, since the economy was sufficiently dominant in its trade relationships to enforce English units on its partners.

#### Creative Applications

1. Do some research! Have there been attempts to change the United States to use the metric system?
2. What is the SI Base unit of electric current?
3. What is kilogram the base unit of?

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