Question

write any five disadvantages of physical quantity​

Answer 1

• Limitations of Dimensional Analysis

• If dimensions are given, physical quantity may not be unique as many physical quantities have same dimensions. ...

• Numerical constant having no dimension (K) such as (1/2), 1 or 2π etc. ...

• The method of dimension can't be used to derive relations other than product of power functions.

• The method of dimension can’t be applied to derive formula if in mechanics a physical quantity depends on more than 3 physical quantities as then there will be less number of equations than the unknowns. However still we can check correctness of the given equation dimensionally. For example: T=2πI/mgl√ can’t be derived by theory of dimensions but its dimensional correctness can be checked.

• Even if a physical quantity depends on three physical quantities, out of which two have same dimensions, the formula can’t be derived by theory of dimensions, e.g., formula for the frequency of a tuning fork f=(d/L2)v can’t be derived by theory of dimensions but can be checked.