Base quantity and Dimensions
Physical Base quantities have the important property that all other derived quantities are derivated algebraically from them. In the SI there are seven base quantities: length (l), mass (m), time (t), electric current (I), Thermodynamic temperature (T), amount of substance (n) and luminous intensity (Iv). By convention, all of these physical quantities are organized in a dimensional system based on the base quantities, each of which is regarded as having its own dimension. The derived quantities will also have dimensions derived algebraically from the seven base quantities by multiplication and division. For example:
The dimension of length is written as[L] and the dimension of time as [T]. When we analyse the dimension of a derived unit such as velocity, which is distance (length) divided by time, then becomes [LT-1] in its notation.
