When an air bubble rises from the bottom of a lake to the surface,its radius is doubled. The atmospheric pressure is equal to that of a column of water of height $H$. The depth of the lake is:

$A$ liquid is taken in a long vertical cylindrical vessel and the cylinder is rotated about its vertical axis as shown in the figure. During rotation, the liquid rises along its sides. If the radius of the vessel is $0.05 \,m$ and the speed of rotation is $10 \,rad \,s^{-1}$, then the height difference between the liquid at the centre of the vessel and its sides is $\left(g=10 \,m \,s^{-2}\right)$.

Write two parts of fluid mechanics and what studies are made in them?

$A$ bottle of soda water is grasped by the neck and swung briskly in a vertical circle. Near which portion of the bottle do the bubbles collect?

$A$ $U$-tube of small and uniform cross-section contains water of total length $4H$. The height difference between the water columns on the left and on the right is $H$ when the valve $K$ is closed. The valve is suddenly opened,and water flows from left to right. Ignore friction. The speed of the water when the heights of the left and the right water columns are the same is:

Which of the following phenomena is not due to surface tension?