At what speed,the velocity head of water is equal to the pressure head of $40 \, cm$ of mercury? (Given: Density of mercury = $13.6 \times 10^3 \, kg/m^3$,Density of water = $10^3 \, kg/m^3$,$g = 9.8 \, m/s^2$)

$A$ barometer kept in a stationary elevator reads $76 \ cm$. If the elevator starts accelerating upwards,the reading will be:

What does it mean when the height of a barometer is rising?

The gauge pressure at a depth of $50 \,m$ in a sea is (Density of sea water is $1025 \,kg \,m^{-3}$ and $g=10 \,ms^{-2}$ ). (in $\,Pa$)

$A$ $U$-shaped tube is partially filled with an incompressible liquid of density $1.2 \ g \ cm^{-3}$. Oil,which does not mix with the liquid,is poured into the left side of the $U$-tube until the liquid rises by $15 \ cm$ on the right side. If the density of the oil is $0.9 \ g \ cm^{-3}$,the oil level will stand higher than the liquid level on the right side of the $U$-tube by: (in $cm$)

The height of a mercury barometer is $75 \ cm$ at sea level and $50 \ cm$ at the top of a hill. The ratio of the density of mercury to that of air is $10^4$. The height of the hill is ....... $km$.