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 $0.016 \times 10^5 \, Pa$.)

When an air bubble of radius $r$ rises from the bottom to the surface of a lake,its radius becomes $5r/4$ (the pressure of the atmosphere is equal to the $10 \, m$ height of water column). If the temperature is constant and the surface tension is neglected,the depth of the lake is .... $m$ (in $.53$)

Why can liquids flow?

$A$ cylindrical vessel containing a liquid is rotated about its axis so that the liquid rises at its sides as shown in the figure. The diameter of the vessel is $10 \, cm$ and the angular speed of rotation is $\omega \, rad \, s^{-1}$. The difference in the height,$h$ (in $cm$),of the liquid at the centre of the vessel and at the side will be

$A$ container of liquid is released from rest on a smooth inclined plane as shown in the figure. The length of the inclined plane is sufficient. Assume the liquid finally reaches equilibrium relative to the container. The final liquid surface makes an angle with the horizontal of ...... $^o$.

$A$ vertical $U-$tube of uniform inner cross-section contains mercury in both sides of its arms. $A$ glycerin (density = $1.3 \text{ g/cm}^3$) column of length $10 \text{ cm}$ is introduced into one of its arms. Oil of density $0.8 \text{ g/cm}^3$ is poured into the other arm until the upper surfaces of the oil and glycerin are in the same horizontal level. Find the length of the oil column in $\text{cm}$. (Density of mercury = $13.6 \text{ g/cm}^3$)