SI derived unit
Let an agent explain SI derived units and their construction, relay the units with special names, coherence and dimensionless units from the SI Brochure, describe their use, and distinguish derived units from base units, non-SI units accepted for use and prefixed units.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent explain SI derived units and their construction, relay the units with special names, coherence and dimensionless units from the SI Brochure, describe their use, and distinguish derived units from base units, non-SI units accepted for use and prefixed units.
A unit of measurement in the International System of Units formed by combining base units, such as the newton, pascal, joule and watt among the 22 coherent derived units with special names, together with derived units expressed only in base units and dimensionless derived units such as the radian and units of ratios of length; derived units are coherent when formed from base units without numerical factors.
What it is for: Expressing derived quantities in SI.
It can be explain construction; relay named and dimensionless units; describe use; distinguish related units.
Distinguishing features
Built from base units
Coherent
Special names
Dimensionless members
What it looks like
Not a visible object; unit symbols such as N, Pa, J and W.
Physical character
SI base units: 7 count
derived units with special names: 22 count
SI Brochure edition: 9th, 2019 note
How it is recognised
SI unit built from base units
Newton, pascal, joule, watt, radian, steradian, per mole, ratios of length
Base units are the seven defined units; accepted non-SI units such as the litre are outside; prefixes scale units
Related models
is a kind of - in registry terms
is a kind of - in registry terms
is built from - by multiplication and division
is exemplified by - the unit of force
In practice
Families and kinds
coherent derived units with special names such as newton, pascal, joule and watt
derived units expressed in base units such as metre per second
dimensionless derived units such as radian and steradian
units of reciprocal amount of substance such as per mole
units of ratios of length such as metre per metre
Identifiers
BIPM SI Brochure chapter 2 derived units
Standards and regulation
SI Brochure of the BIPM
ISO 80000 quantities and units
National metrology regulations
Failure modes and hazards
Confusing derived with base units
Misusing non-coherent units
Registry aliases naming unit categories rather than units
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Understand What SI derived units are.
Science.
Definition
Definition.
Definition
Definition.
- What is an SI derived unit, and how does it differ from base units, accepted non-SI units and prefixed units? definition
- Is the question about the category, a specific unit or a conversion? boundary
Named
Named units.
Named
Named.
- What are the 22 derived units with special names, and what quantities do they measure? definition
- Which entry fits the specific unit? action
Theory Coherence and dimension.
Science.
Coherence
Coherence.
Coherence
Coherence.
- What does coherence mean, and why does it matter in calculations? provenance
- Which references are standard? provenance
Dimensionless
Dimensionless units.
Dimensionless
Dimensionless.
- How are the radian, steradian and ratio units treated in the SI? provenance
- Which sources are cited? provenance
Use Use.
Practice.
Writing
Writing units.
Writing
Writing.
- How are derived units written, combined and prefixed correctly? action
- Which entry fits SI unit symbols? action
Conversion
Conversion.
Conversion
Conversion.
- How are derived units converted from other systems? action
- Which entry fits unit conversion? action
Context History.
Context.
History
History.
History
History.
- How did the SI derived units develop, and what changed in the 2019 redefinition? provenance
- Which entry fits the 2019 redefinition of the SI base units? action
Bodies
Governing bodies.
Bodies
Bodies.
- What roles do the BIPM, CGPM and national institutes play? provenance
- Which entry fits International Bureau of Weights and Measures? action
What the second pass must settle
- Should the 22 named units be linked individually?
- How should the SI Brochure be linked?
- The registry entry has merged aliases naming categories of derived units; should they be split off?