A tall cylinder is filled with viscous oil. A round pebble is dropped from the top with zero initial velocity. From the plot shown in figure, indicate the one that represents the velocity $(v)$ of the pebble as a function of time $(t)$.

Which of the following diagrams does not represent a streamline flow?

Along a streamline

An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters 2.5 cm and 3.75 cm . The ratio of the velocities in the two pipes is

The angle of contact at the interface of water-glass is $0^{\circ}$, ethyl alcohol-glass is $0^{\circ}$, mercury-glass is $140^{\circ}$ and methyliodide-glass is $30^{\circ}$. A glass capillary is put in a trough containing one of these four liquids. It is observed that the meniscus is convex. The liquid in the trough is