The value of $g$ at a place decreases by $2\%$. The barometric height of mercury:

When an airplane flies at a higher altitude,it is not advisable to keep a fountain pen in one's pocket. Why?

$A$ sudden drop in the mercury level by $10 \,mm$ or more is a sign of ..........

Who devised for the first time,a method for measuring atmospheric pressure?

In a cylindrical container open to the atmosphere from the top,a liquid is filled up to a $10\, m$ depth. The density of the liquid varies with depth $h$ from the surface as $\rho(h) = 100 + 6h^2$,where $h$ is in meters and $\rho$ is in $kg/m^3$. The pressure at the bottom of the container will be: (Atmospheric pressure $P_0 = 10^5\, Pa$,$g = 10\, m/s^2$)

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 = $10^3 \, kg/m^3$,$g = 9.8 \, m/s^2$)