Consider a rain drop falling at terminal speed. For what radius $\left(R\right)$ of the drop can we disregard the influence of gravity on its shape? Surface tension and density of water are $T$ and $\rho$ respectively.

A barometer contains two uniform capillaries of radii $5.0\times {10}^{-4} m$ and $1.0\times {10}^{-3} m$. If the height of liquid in narrow tube is $0.2 m$ more than that in the wide tube, calculate the true pressure difference. (Given: Density of liquid $={10}^3 kg{ m}^{-3}$, surface tension $=75\times {10}^{-3} N{ m}^{-1}$
angle of contact $=0°$ and $g=10 m{s}^{-2}$.

A false statement is:

A viscous fluid is flowing through two horizontal pipes. The pressure difference $P_2-P_1$ between the ends of each pipe is the same. The pipes have the same radius, although one is twice as long as the other. How does the volume flow rate $Q_B$ in the longer pipe compare with the rate $Q_A$ in the shorter pipe?

A man is rowing a boat with a constant velocity ' $v_0$ ' in a river. The contact area of boat is 'A' and coefficient of viscosity is $\eta$. The depth of river is ' $D$'. Find the force required to row the boat.