$A$ liquid flows through a pipe with a pressure difference of $P$. What should be the pressure difference required to maintain the same flow rate if the radius is doubled and the length is doubled?

$A$ 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 volume of a liquid is proportional to......,given its density $\rho$,viscosity $\eta$ and $t$ the time of flow through a capillary tube of length $L$ and radius $R$,with a pressure difference $p$ across its ends.

What is Reynolds number?

Two liquids of densities $d_1$ and $d_2$ are flowing in identical capillary tubes under the same pressure difference. If $t_1$ and $t_2$ are the times taken for the flow of equal quantities (mass) of liquids,then the ratio of the coefficient of viscosity of the liquids must be:

Two tubes of radii $r_1$ and $r_2$,and lengths $l_1$ and $l_2$,respectively,are connected in series and a liquid flows through each of them in streamline conditions. $P_1$ and $P_2$ are pressure differences across the two tubes. If $P_2 = 4P_1$ and $l_2 = \frac{l_1}{4}$,then the radius $r_2$ will be equal to: