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3 System of Units
The derived unit of measurement: the unit of measurement of the derived quantity in a given system of quantities.
Consistent unit of measurement: this may be expressed as the product of powers
of base units with a coefficient of proportionality equal to one; for example, in SI,
the consistent unit w is 1 N 1 m kg s
−2 .
Unit of measurement outside of the system: this does not belong to the system
of units, for example, day, hour, minute are units of time outside the SI.
Dimensionless unit of measurement: the derived unit of measurement with a
dimension of one; for example, a unit of plane angle (radian; rad) or solid angle
(steradian; sr).
Legal unit of measurement: the unit of measurement, the application of which
is required or permitted by legislation.
The system of units: an ordered set of units of measurement, created on the basis
of the conventionally adopted base quantities and with assigned units of measurement
and set equations used to define the derived quantities.
A coherent system of units of measurement: derived units of measurement are
expressed by base units with a formula with a numerical coefficient of one.
The equation of units: specifies the units for derived quantities in a certain system
of units through base and other derived units of the said system; for example, 1 m
2
1 m · 1 m, 1 W 1 V · 1 A. Also establishes the relationship between the unit of
measurement of a certain size and its multiple or sub-multiple; for example, 1 mm
0.001 m, 1 pF 10
−12 F. Determines the equivalence between the measurement
units of the same quantity in the different systems of units; for example, 1 kg
1 kg · 9.80665 m/s
2
9.80665 N.
3.6 Fundamental Physical Constant
The fundamental physical constants act as universal coefficients binding certain quantities. They are present in the equations expressing the laws of nature in the form of
products of powers of base quantities.
Characteristics of constants:
– Generally believed to be both universal in nature and having constant value in
time;
– It is unlike a mathematical constant, which has a fixed numerical value, but does
not directly involve any physical measurement;
– They have assigned units of measurement;
– Their values do not change in the adopted system of units of measurement;
– In the quantitative equations, they are treated as individual quantities;
– Immutable parameters of the universe influence their actual form.
The fundamental values of the constants are recommended by the Committee
on Data for Science and Technology (CODATA). The CODATA Task Group on
Fundamental Physical Constants has been publishing recommended values for the
Fundamental Physical Constants since 1969. The most updated information can
3 System of Units
The derived unit of measurement: the unit of measurement of the derived quantity in a given system of quantities.
Consistent unit of measurement: this may be expressed as the product of powers
of base units with a coefficient of proportionality equal to one; for example, in SI,
the consistent unit w is 1 N 1 m kg s
−2 .
Unit of measurement outside of the system: this does not belong to the system
of units, for example, day, hour, minute are units of time outside the SI.
Dimensionless unit of measurement: the derived unit of measurement with a
dimension of one; for example, a unit of plane angle (radian; rad) or solid angle
(steradian; sr).
Legal unit of measurement: the unit of measurement, the application of which
is required or permitted by legislation.
The system of units: an ordered set of units of measurement, created on the basis
of the conventionally adopted base quantities and with assigned units of measurement
and set equations used to define the derived quantities.
A coherent system of units of measurement: derived units of measurement are
expressed by base units with a formula with a numerical coefficient of one.
The equation of units: specifies the units for derived quantities in a certain system
of units through base and other derived units of the said system; for example, 1 m
2
1 m · 1 m, 1 W 1 V · 1 A. Also establishes the relationship between the unit of
measurement of a certain size and its multiple or sub-multiple; for example, 1 mm
0.001 m, 1 pF 10
−12 F. Determines the equivalence between the measurement
units of the same quantity in the different systems of units; for example, 1 kg
1 kg · 9.80665 m/s
2
9.80665 N.
3.6 Fundamental Physical Constant
The fundamental physical constants act as universal coefficients binding certain quantities. They are present in the equations expressing the laws of nature in the form of
products of powers of base quantities.
Characteristics of constants:
– Generally believed to be both universal in nature and having constant value in
time;
– It is unlike a mathematical constant, which has a fixed numerical value, but does
not directly involve any physical measurement;
– They have assigned units of measurement;
– Their values do not change in the adopted system of units of measurement;
– In the quantitative equations, they are treated as individual quantities;
– Immutable parameters of the universe influence their actual form.
The fundamental values of the constants are recommended by the Committee
on Data for Science and Technology (CODATA). The CODATA Task Group on
Fundamental Physical Constants has been publishing recommended values for the
Fundamental Physical Constants since 1969. The most updated information can