Write and explain principle of homogeneity. Check dimensional consistency of given equation.
Magnitude of physical quantities having same dimension can be added together or subtracted from one another.
This principle is called principle of homogeneity of dimension.
This rule is very useful to check dimensional consistency of given equation.
To check dimensional consistency of given equation all terms on both side of the equation should have same dimension.
Dimensional consistency do not guarantee correctness of equation.
It is uncertain to the extent of dimensionless quantities or function.
For example,
$x=x_{0}+v_{0} t+\frac{1}{2} a t^{2}$
Here, $x$ is distance covered by object in time $t$.
$x_{0}=\text { initial position of object during motion }$
$x=\text { final position }$
$v_{0}=\text { initial velocity }$
$a=\text { acceleration }$
$\text { LHS }=x=\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{0}$
In $RHS$ there are three terms,
$x_{0}=\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{0}$
$v_{0} t=\left[\mathrm{L}^{1} \mathrm{~T}^{-1}\right]\left[\mathrm{T}^{1}\right]=\mathrm{M}$$^{0} \mathrm{~L}^{1} \mathrm{~T}^{0}$
In $\frac{1}{2} a t^{2}$ is constant term which is dimensionless.
$\therefore a t^{2} =\left[\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{-2}\right]\left[\mathrm{T}^{2}\right]$
$=\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{0}$
Here all terms in given equation have same dimension. Hence, given equation,
Consider following statements
$(A)$ Any physical quantity have more than one unit
$(B)$ Any physical quantity have only one dimensional formula
$(C)$ More than one physical quantities may have same dimension
$(D)$ We can add and subtract only those expression having same dimension
Number of correct statement is
In a particular system of units, a physical quantity can be expressed in terms of the electric charge $c$, electron mass $m_c$, Planck's constant $h$, and Coulomb's constant $k=\frac{1}{4 \pi \epsilon_0}$, where $\epsilon_0$ is the permittivity of vacuum. In terms of these physical constants, the dimension of the magnetic field is $[B]=[c]^\alpha\left[m_c\right]^\beta[h]^\gamma[k]^\delta$. The value of $\alpha+\beta+\gamma+\delta$ is. . . . .
If orbital velocity of planet is given by $v = {G^a}{M^b}{R^c}$, then
The equation $\frac{{dV}}{{dt}} = At - BV$ is describing the rate of change of velocity of a body falling from rest in a resisting medium. The dimensions of $A$ and $B$ are