Which of the following quantities has the dimensions of $\frac{\pi P r^4}{8 Q l}$? (Where $P =$ pressure,$r =$ radius,$Q =$ volume flow rate in $m^3/s$,and $l =$ length.)

$A$ fluid of density $\rho$ and viscosity $\eta$ is flowing through a pipe of diameter $d$, with a velocity $v$. The Reynolds number is:

If it takes $5\,minutes$ to fill a $15\,litre$ bucket from a water tap of diameter $\frac{2}{\sqrt{\pi}}\,cm$,then the Reynolds number for the flow is (density of water $= 10^3\,kg/m^3$ and viscosity of water $= 10^{-3}\,Pa\cdot s$) close to

Water is flowing through a very narrow tube. The velocity of water below which the flow remains a streamline flow is known as

Which of the ratio of forces represents the Reynolds number $Re$?

Two capillaries of same length and radii in the ratio $1:2$ are connected in series. $A$ liquid flows through them in a streamlined condition. If the pressure across the two extreme ends of the combination is $1 \ m$ of water,the pressure difference across the first capillary is...... $m$.