Reference Notes
Four Categories of Physical Quantities
Unit: Units and Measurement
Science | Physics Class 11

Four Categories of Physical Quantities
Physical quantities are categorized into four types:

(i) Dimensional variables: Physical quantities which have dimensions but do not have fixed value are called the dimensional variables. Examples are work, power, velocity etc.

(ii) Dimensionless variables: These are physical quantities which have neither dimensions nor fixed value. Some examples are strain, specific gravity.

(iii) Dimensional constants: These are the physical quantities which have dimensions and fixed value. Their examples are gravitational constant, velocity of light etc.

(iv) Dimensionless constants: Physical quantities which do not possess dimensions but have fixed value are called dimensionless constants. Examples are π, counting number etc.