Consider a water tank shown in the figure. It has one wall at x = L and can be taken to be very wide in the z direction. When filled with a liquid of surface tension S and density \rho, the liquid sur

Question

Consider a water tank shown in the figure. It has one wall at $x = L$ and can be taken to be very wide in the $z$ direction. When filled with a liquid of surface tension $S$ and density $ρ$ , the liquid surface makes an angle $θ_{0}$ ( $θ_{0} ≪ 1$ ) with the $x$ -axis at $x = L$ . If $y (x)$ is the height of the surface, then the equation for $y (x)$ is (take $sin θ (x) \approx tan θ (x) \approx \frac{d y}{d x}$ ; $g$ is the acceleration due to gravity):

Question 1 as printed in the NEET 2025 booklet

![Question 1 as printed in the NEET 2025 booklet](/figures/neet-2025/q1.png)

Vishal Gupta · Accepted Answer

B. At height y the hydrostatic pressure ho g y is balanced by the surface-tension pressure S 	imes (curvature). For a nearly flat surface the curvature is \frac{d^2y}{dx^2}, so S\frac{d^2y}{dx^2} = ho g\,y, i.e. \frac{d^2y}{dx^2} = \frac{ho g}{S}y.

Mechanical Properties of Fluids

More from this chapter in past papers