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

$Assertion :$ For Reynolds number $Re > 2000$, the flow of fluid is turbulent.
$Reason :$ Inertial forces are dominant compared to the viscous forces at such high Reynolds numbers.

What is critical velocity? Write a formula for critical velocity.

Two different liquids flow through tubes of the same radius. If the ratio of their coefficients of viscosity is $52:49$ and the ratio of their densities is $13:1$,what is the ratio of their critical velocities?

$A$ highly viscous liquid of viscosity coefficient $\eta$ flows through a fixed horizontal cylindrical tube (fixed from the outer surface) of internal radius $r$,thickness $t$ $(t \ll r)$,and length $l$. The volume of liquid flowing per second is $Q$ and the pressure difference across the tube is $P$. If the modulus of rigidity of the material of the tube is $\beta$,the shear strain in the tube will be:

The rate of steady volume flow of water through a capillary tube of length $l$ and radius $r$,under a pressure difference of $p$ is $V$. This tube is connected with another tube of the same length but half the radius,in series. Then,the rate of steady volume flow through them is (The pressure difference across the combination is $p$.)