lesson
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In 1999, NASA lost the $125 million Mars Climate Orbiter because one engineering team calculated thruster force in English pounds while the navigation team expected metric newtons.
To prevent costly errors and communicate universally, scientists rely on the International System of Units (SI), built from seven fundamental standards.
The Seven SI Base Units
A base unit is an independent standard measurement that cannot be defined in terms of other physical quantities.
Every physical quantity in the universe can be described by combining these seven fundamental units.
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What happens when we measure quantities that aren't on this list of seven, like speed, force, or energy?
Building Derived Units
A derived unit is formed by multiplying or dividing base units according to the mathematical definition of a physical quantity.
For example, speed is distance traveled divided by time, giving the derived unit meters per second (m/s or mβ
sβ1).
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How do we break down complex named units like the newton or the joule into their fundamental base components?