The atmospheric pressure and height of the barometer column are $10^5 \, Pa$ and $760 \, mm$ respectively on the Earth's surface. If the barometer is taken to the Moon,then the column height will be ........ $mm$.

$A$ barometer tube,containing mercury,is lowered in a vessel containing mercury until only $50 \, cm$ of the tube is above the level of mercury in the vessel. If the atmospheric pressure is $75 \, cm$ of mercury,what is the pressure at the top of the tube?

$A$ container of height $10 \, cm$ is filled with water. There is a hole at the bottom. Find the pressure difference between points at the top and the bottom.

$A$ manometer reads the pressure of a gas in an enclosure as shown in the figure. The absolute and gauge pressure of the gas in $cm$ of mercury are (Take atmospheric pressure $= 76\,cm$ of mercury)

$A$ barometer is kept in an elevator accelerating downwards with an acceleration $a$. What is the most likely pressure reading inside the elevator?

Consider the wall of a dam to be straight with height $H$ and length $L$. It holds a lake of water of height $h$ $(h < H)$ on one side. Let the density of water be $\rho_w$. Denote the torque about the axis along the bottom length of the wall by $\tau_1$. Denote also a similar torque due to the water up to height $h/2$ and wall length $L/2$ by $\tau_2$. Then $\tau_1 / \tau_2$ (ignore atmospheric pressure) is