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When that multiplier is one, the unit is called a coherent derived unit. For example, the coherent derived SI unit of velocity is the metre per second, with the symbol m/s. [1]: 139 The base and coherent derived units of the SI together form a coherent system of units (the set of coherent SI units). A useful property of a coherent system is ...
The atomic units have been chosen to use several constants relating to the electron: the electron mass, the elementary charge, the Coulomb constant and the reduced Planck constant. The unit of energy in this system is the total energy of the electron in the Bohr atom and called the Hartree energy. The unit of length is the Bohr radius.
A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. [1] Any other quantity of that kind can be expressed as a multiple of the unit of measurement. [2] For example, a length is a physical quantity.
List of humorous units of measurement; List of unusual units of measurement; List of obsolete units of measurement; List of measuring instruments; List of nautical units of measurement; List of scientific units named after people; List of international units; List of SI electromagnetism units
Units of measurement are generally defined on a scientific basis, overseen by governmental or independent agencies, and established in international treaties, pre-eminent of which is the General Conference on Weights and Measures (CGPM), established in 1875 by the Metre Convention, overseeing the International System of Units (SI). For example ...
This is a list of units of measurement based on human body parts or the attributes and abilities of humans (anthropometric units). It does not include derived units further unless they are also themselves human-based. These units are thus considered to be human scale and anthropocentric.
A quantity equation, also sometimes called a complete equation, is an equation that remains valid independently of the unit of measurement used when expressing the physical quantities. [ 28 ] In contrast, in a numerical-value equation , just the numerical values of the quantities occur, without units.
The earliest units of measure devised by humanity bore no relationship to each other. [citation needed] As both humanity's understanding of philosophical concepts and the organisation of society developed, so units of measurement were standardized—first particular units of measure had the same value across a community, then different units of the same quantity (for example feet and inches ...