Units and Dimensions

UNITS AND DIMENSIONS

In general, units and dimensions are used in dimensional analysis. Dimensional analysis is a mathematical technique which uses the dimensions of quantities in solving the engineering problems in fluid mechanics. There are three fundamental dimensions viz., length, mass and time. All physical quantities are measured making use of dimensions.

Physical quantities which are expressed in terms of length (L) mass (M) and time (T) are called fundamental quantities and the quantities which can be expressed in terms of the primary quantities are called derived or secondary quantities. An arbitrarily fixed value to measure each dimensions or quantities is called a unit. The arbitrary fixed values are used to measure primary dimension are called primary units. The units which are derived from primary units are called derived units.