Units and Measurement: Physical Quantities

Physical Quantities

Those quantities in terms of which physics is studies and which can be measured directly or indirectly are called physical quantities

Ex.: mass, force, speed, acceleration etc.

Fundamental and derived physical quantities

Physical quantities are often divided into fundamental and derived quantities.  In physics, there are seven fundamental or base quantities.  These are : Mass, length, time, temperature, electric current, luminous intensity and amount of substance.  These are called fundamental quantities because;

1. These are the simplest physical quantities and cannot be broken into more simple physical quantities.
2. All other quantities can be obtained only from these.

Thus, it is clear that fundamental quantities are not defined in terms of other physical quantities and these are independent of other physical quantities

All other quantities (except fundamental quantities) which can be expressed in terms of some suitable combination of seven fundamental quantities are called derived physical quantities.   As all physical quantities are expressed in terms of fundamental quantities, therefore, fundamental quantities or base quantities are called seven dimensions of the physical world.