$A$ liquid is flowing in a horizontal uniform capillary tube under a constant pressure difference $P$. The value of pressure for which the rate of flow of the liquid is doubled when the radius and length both are doubled is

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?

What is the value of Reynolds number for turbulent flow?

$A$ horizontal pipeline carrying gasoline has a cross-sectional diameter of $5 \,mm$. If the viscosity and density of the gasoline are $6 \times 10^{-3} \,Poise$ and $720 \,kg/m^3$ respectively, the velocity after which the flow becomes turbulent is:

Water is conveyed through a uniform tube of $8 \text{ cm}$ in diameter and $3140 \text{ m}$ in length at the rate of $2 \times 10^{-3} \text{ m}^3/\text{s}$. The pressure required to maintain the flow is (Viscosity of water $= 10^{-3} \text{ SI units}$):

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 $p$.)