$A$ liquid $X$ of density $3.36 \ g/cm^3$ is poured into a $U$-tube, which contains $Hg$. Another liquid $Y$ is poured into the left arm with a height of $8 \ cm$. The upper levels of $X$ and $Y$ are at the same height. What is the density of $Y$ in $g/cc$?

At every point of a liquid at rest,the tangential stress is zero. Explain with reason.

In which layer of the atmosphere is water vapour present?

In the figure, chamber $A$ contains a gas, a movable chamber $B$ is placed on top of the gas and it contains $n$ metal balls. The weight of chamber $B$ and the balls is supported by the gas. Chamber $C$ is a vacuum. Let the gas be in equilibrium at pressure $P$. Let $P^{\prime}$ be the pressure if one of the balls is taken away. Find $(P-P^{\prime}) / P$.

In the previous problem,if $15.0 \; cm$ of water and spirit each are further poured into the respective arms of the tube,what is the difference in the levels of mercury in the two arms (in $; cm$)? (Specific gravity of mercury $= 13.6$)

Gauge pressure is defined as: