In the case of a fluid flowing on a horizontal surface, the flow of the fluid becomes unsteady when the Reynolds number $(R_n)$ is:

Water flows in a streamline manner through a capillary tube of radius $a$. The pressure difference is $P$ and the rate of flow is $Q$. If the radius is reduced to $\frac{a}{4}$ and the pressure is increased to $4P$,then the rate of flow becomes ................

Consider an increase of $1 \%$ in each of the radius of the artery, the viscosity of blood, and the density of blood, respectively. The percentage change in the flow rate of blood in the artery is (in $\%$)

$A$ 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:

$A$ capillary tube of length $l$ and radius $r$ is connected to the bottom of a container. When the pressure difference across it is $P$,the volume of water flowing out per second is $V$. If another capillary tube of the same length but half the radius is connected in series with the first one,what will be the new volume of liquid flowing out per second? (The total pressure difference across the system is $P$.)

Two capillary tubes of the same length but different radii $r_1$ and $r_2$ are fitted in parallel to the bottom of a vessel. The pressure head is $P$. What should be the radius of a single tube that can replace the two tubes so that the rate of flow is the same as before?