During a blood transfusion,a needle is inserted into a vein where the gauge pressure is $2000\,Pa$. At what height must the blood container be placed so that blood may just enter the vein (in $,m$)? (Density of blood $= 1.06 \times 10^3\,kg/m^3$ and take $g = 9.8\,m/s^2$).

Explain why you cannot make a decent cup of tea on a mountain.

$A$ submarine experiences a pressure of $5.05 \times 10^6 \, Pa$ at a depth of $d_1$ in a sea. When it goes further to a depth of $d_2,$ it experiences a pressure of $8.08 \times 10^6 \, Pa.$ Then $d_2 - d_1$ is approximately ........ $m$ (density of water $= 10^3 \, kg/m^3$ and acceleration due to gravity $= 10 \, m/s^2$).

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

The pressure at a point $10 \ m$ below the surface of water is (take atmospheric pressure $P_0 = 1.01 \times 10^5 \ Nm^{-2}$ and $g = 10 \ ms^{-2}$):

By sucking through a straw,a student can reduce the pressure in his lungs to $750\, mm$ of $Hg$ (density $= 13.6\, g/cm^3$). Using the straw,he can drink water from a glass up to a maximum depth of ....... $cm$.