The dimensional formula for $r.m.s.$ (root mean square) velocity is

$Assertion$ : The dimensional formula for relative velocity is the same as that of the change in velocity.
$Reason$ : Relative velocity of $P$ with respect to $Q$ is the ratio of the velocity of $P$ and that of $Q$.

The amount of solar energy received on the Earth's surface per unit area per unit time is defined as the solar constant. The dimension of the solar constant is:

The dimensional formula of a physical quantity represented by $\frac{e^2}{4 \pi \varepsilon_0 \hbar}$ is (where $e$ is the charge of an electron,$\varepsilon_0$ is the permittivity of free space,and $\hbar$ is the reduced Planck's constant). Note: The expression $\frac{e^2}{4 \pi \varepsilon_0 \hbar}$ is equivalent to the fine-structure constant $\alpha$ multiplied by the speed of light $c$.

The dimensions of permeability of free space $(\mu_0)$ can be given by:

Turpentine oil is flowing through a tube of length $l$ and radius $r$. The pressure difference between the two ends of the tube is $P$. The viscosity of oil is given by $\eta = \frac{P(r^2 - x^2)}{4vl}$,where $v$ is the velocity of oil at a distance $x$ from the axis of the tube. The dimensions of $\eta$ are