A spherical body of mass $m$ and radius $r$ is allowed to fall in a medium of viscosity $\eta $. The time in which the velocity of the body increases from zero to $0.63$ times the terminal velocity $(v)$ is called time constant $(\tau )$. Dimensionally $\tau $ can be represented by
$\frac{{m{r^2}}}{{6\pi \eta }}$
$\sqrt {\left( {\frac{{6\pi mr\eta }}{{{g^2}}}} \right)} $
$\frac{m}{{6\pi \eta rv}}$
None of the above
The physical quantity which has the dimensional formula ${M^1}{T^{ - 3}}$ is
What is dimension of physical quantities ? Explain by using suitable example.
Let $[ {\varepsilon _0} ]$ denote the dimensional formula of the permittivity of vacuum. If $M =$ mass, $L=$ length, $T =$ time and $A=$ electric current, then:
A dimensionally consistent relation for the volume $V$ of a liquid of coefficient of viscosity $\eta $ flowing per second through a tube of radius $r$ and length $l$ and having a pressure difference $p$ across its end, is
A physical quantity of the dimensions of length that can be formed out of $c, G$ and $\frac{e^2}{4\pi \varepsilon _0}$ is $[c$ is velocity of light, $G$ is the universal constant of gravitation and $e$ is charge $] $