A numerical-value equation is an equation between
quantities in which just the values of the quantities occurs but not the
unit of measurement
A unit of measurement 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. Any other quantity of that kind can be expressed as a mult ...
. Therefore, the
equation requires to be used with the values the quantity has in a specific unit. A numerical value equation always has to be marked as such.
Numerical value equations are in contrast to quantity equations. Quantity equations hold independently of the unit used to express the value of the quantity.
For example, a quantity equation for
displacement
Displacement may refer to:
Physical sciences
Mathematics and Physics
*Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...
''d'' as
speed
In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity ...
''s'' multiplied by time difference ''t'' would be:
:''d''=''s'' ''t''
for ''s''=5m/s and ''t'' and ''d'' in any units.
In contrast, a numerical-value equation would be:
:''D''=5 ''T''
for ''T'' in seconds and ''D'' in metres.
Generally, the use of numerical value equations is discouraged.
See also
*
Dimensional analysis
In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their base quantities (such as length, mass, time, and electric current) and units of measure (such as ...
References
{{Reflist
Physical quantities