Physical quantities that have the same dimensions may be added or subtracted. Comprehensive understanding of dimension analysis allows one to deduce certain relationships between different physical dimensions and to check derivation, accuracy and dimensional homogeneity.
According to the Principle of Homogeneity, the dimensions of each term of a dimensional equation on both sides should be the same. This theory allows us to convert the units from one form to another.
Given that
Time period of oscillations = T
T depends on length (l), mass and acceleration due to gravity
T \propto l^x g^y m^z
T=k\ l^x\ g^y\ m^z where, k- constant ....................(1)
Step 1: Dimensional formula for given equation
LHS side: T = seconds
Dimensional formula [math] T = [L^0 T^{1} M^0] [/math]
RHS side: =k\ l^x\ g^y\ m^z
Dimensional formula [math] = [L^1]^x [L^1 T^{-2}]^y [M]^z [/math]
[math] = [L^x L^y T^{-2y} M^z] [/math]
[math]=[\ L^{x+y}\ T^{-2y}\ M^{\ z}\ ][/math]
LHS = RHS
[math] [L^0 T^{1} M^0] = [L^{x+y} T^{-2y } M^z] [/math]
Step 2: Deriving the equation for time period of oscillations
Equate the dimensions on both side of the dimensional equation
x + y = 0 ,
-2y=1\ \Rightarrow y = \frac{-1}{2}
z = 0
x + \frac{-1}{2} = 0 \Rightarrow x = \frac{1}{2}
Substituting x, y and z value in equation (1)
Time equation T = k l^{\frac{1}{2}} g^\frac{-1}{2} m^0
T = k \frac{\sqrt{l}}{\sqrt{g}}
T = k \sqrt{\frac{l}{g}}