The relative humidity on a day,when the partial pressure of water vapour is $0.012 \times 10^5 \, Pa$ at $12^{\circ}C$,is ......... $\%$. (Take the vapour pressure of water at this temperature as $0.016 \times 10^5 \, Pa$.)

$A$ liquid kept in a cylindrical vessel is rotated about a vertical axis passing through the center of the circular base. The difference in the heights of the liquid at the center of the vessel and its edge is ($R=$ radius of vessel,$\omega=$ angular velocity of rotation,$g=$ acceleration due to gravity).

Fill in the blanks:
$(i)$ The surface tension of water at critical temperature is ......
$(ii)$ Bernoulli's equation is based on the conservation of ......
$(iii)$ The energy would be ...... if $1$ large drop of water splits into $8$ small drops of water.
$(iv)$ When strong wind passes over a building,the force acting on the building is in the ......

Why can liquids flow?

$A$ 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 $\left(g=10 \,m \,s^{-2}\right)$.

$A$ cylindrical tank of height $1 \ m$ and cross-sectional area $A = 4000 \ cm^2$ is initially empty. It is kept under a tap of cross-sectional area $a_1 = 1 \ cm^2$. Water starts flowing from the tap at $t = 0$ with a speed $v_1 = 2 \ m/s$. There is a small hole in the base of the tank of cross-sectional area $a_2 = 0.5 \ cm^2$. The variation of the height of water in the tank (in meters) with time $t$ is best depicted by: