Two mercury droplets of radii 0.1 cm. and 0.2 cm. collapse into one single drop. What amount of energy is released? The surface tension of mercury T= 435.5 * 10^-3 Nm^-1 .

Surface tension is the force acting on the surface of the liquid.

Bernoulli's principle states that in a steady flow, the sum of pressure, kinetic energy per unit volume, and potential energy per unit volume remains constant.

Yes, the Mechanical properties of fluids class 11th physics is important in NEET. On average, 1-2 questions would be asked from this chapter, which you can cover from the Class 11th Mechanical Properties of Fluids notes.

The main mechanical properties of fluids are exerting pressure, resisting flow or viscosity, forming surface tension, following Bernoulli's principle, and moving in a streamline.

Since velocity does not change, so acceleration will be zero.

mg = FB + Fv $\Rightarrow \frac{4\pi }{3}{r}^3\rho g=\frac{4\pi }{3}{r}^3\sigma g+6\pi \eta rv$

$\Rightarrow v=\frac{2r^2\left(\rho -\sigma \right)g}{9\eta }=\frac{2\times 0.1\times 0.1\times 10^{-6}\times \left(10^4-10^3\right)\times 10}{9\times 1.0\times 10^{-5}}$

$\Rightarrow h=\frac{400}{2g}=20m$