Base unit
Definition
A base unit is a fundamental unit of measurement defined by a physical standard, from which other units are derived. Examples include the meter for length and the kilogram for mass.
5 Must Know Facts For Your Next Test
- The International System of Units (SI) has seven base units: meter, kilogram, second, ampere, kelvin, mole, and candela.
- Base units are essential for defining derived units through mathematical relationships.
- The meter was originally defined as one ten-millionth of the distance from the equator to the North Pole along a meridian.
- In 2019, the definition of the kilogram was updated to be based on Planck's constant rather than a physical object.
- Base units provide standardized measurements that ensure consistency in scientific calculations globally.
Review Questions
- What are the seven SI base units?
- How does a base unit differ from a derived unit?
- Explain why it was significant to redefine the kilogram based on Planck's constant.
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Related terms
Derived Unit: A unit of measurement derived from one or more base units through mathematical operations. Examples include meters per second (m/s) for velocity and joules (J) for energy.
International System of Units (SI): The modern form of the metric system, consisting of seven base units and their derived counterparts used worldwide for scientific measurements.
Planck's Constant: A fundamental constant ($h$) used in quantum mechanics, with dimensions of action (energy multiplied by time), crucial in redefining the kilogram.
