Name: si base units behind measured quantities
Uploaded: 2023-04-30T10:47:58.000Z
Duration: 1 min 14 s
Channel: JoVE

K12 Standards

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Physical Science

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Base Quantities and Derived Quantities

Physical quantities can be divided into base quantities and derived quantities. Base quantities can be expressed through a measurement process, and their units are known as base units.
For example, the distance between two points is measured in terms of meters. Here the base quantity is the distance, and the unit used to measure it is the meter, which is the base unit.
The physical quantities obtained from the combinations of base quantities are known as derived quantities, and the units used to define these quantities are known as derived units.
For example, the speed of a moving car from one point to another is defined as the distance traveled divided by travel time. Here, speed is a derived quantity obtained from the base quantities distance and time.
The unit of speed is meters per second, the derived unit from the base units, meters, and seconds. All the derived quantities and derived units are defined from base quantities and base units, respectively.

base quantities and derived quantities

In any system of units, the units for some physical quantities must be specified through a measurement process. These measurements are the base quantities of the system, and their units are the base units of the system. The algebraic combinations of the base values can then be used to express all other physical quantities. Each of these physical quantities is then referred to as a derived quantity, with each unit being referred to as a derived unit.
The International Organization for Standardization recommends using seven base quantities, which form the International System of Quantities (ISQ). All the other physical quantities can be expressed as combinations of these seven base physical quantities. For example, in geometry, the concept of area is always calculated as the product of two lengths. Thus, area is a derived quantity that can be expressed in terms of SI base units using square meters. Meanwhile, density is defined as mass divided by volume, which is expressed as kilograms per cubic meter (kg/m3) in terms of SI base units. In summary, all physical quantities can be derived from the seven base quantities, and the units of all the physical quantities can be derived from the seven SI base units.
This text is adapted from <a href="https://openstax.org/books/university-physics-volume-1/pages/1-2-units-and-standards">Openstax University Physics Volume 1, Section 1.2 Units and Standards. </a>

In any system of units, the units for some physical quantities must be specified through a measurement process. These measurements are the base quantities ...

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si base units behind measured quantities

SI base units are the starting point for measuring physical quantities. In any system of units, some quantities must be defined through direct measurement. These are called base quantities, and their units are base units.

Other physical quantities are built from these base values by algebraic combinations. These are called derived quantities, and their units are derived units. For example, area comes from two lengths multiplied together. It is a derived quantity and is written in SI base units as square meters.

The International Organization for Standardization recommends seven base quantities. Together, they make up the International System of Quantities, or ISQ. Every other physical quantity can be expressed as a combination of these seven base physical quantities. Density is one example. It is mass divided by volume and is written in SI base units as kilograms per cubic meter, or kg/m^3.

In this way, the seven SI base units provide the foundation for every other unit. Once the base quantities are known, derived quantities and derived units can be written from them. This idea helps connect common measurements like area and density to the full SI system.

SI Base Units Behind Measured Quantities

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SI base units are the starting point for measuring physical quantities. In any system of units, some quantities must be defined through direct measurement. These are called base quantities, and their units are base units. Other physical quantities are built from these base values by algebraic combinations. These are called derived quantities, and their units are derived units. For example, area comes from two lengths multiplied together. It is a derived quantity and is written in SI base units...

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Learn how base quantities, base units, derived quantities, and derived units connect in the SI system, with examples like area and density.

SI Base Units Behind Measured Quantities | JoVE K12

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SI Base Units Behind Measured Quantities

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