Question

By sucking through a straw, a boy can reduce the pressure in his lungs to $750mm$ of $Hg$ (density$=13.6g/c{m}^3$). Using a straw, he can drink water from a maximum depth of

• A. $13.6cm$
• B. $1.36cm$
• C. $0.136cm$
• D. $10cm$

Answer 1

The correct option is A $13.6cm$

Given Pressure in lungs$P_{lungs}=750$ mm of Hg

and atmospheric pressure$P_{atm}=760$ mm of Hg

Now pressure difference $\Delta P=760-750=10$ mm of Hg=1 cm of Hg

Now

1 cm of Hg$={\rho }_{water}gh$

$1{\rho }_{Hg}g={\rho }_{water}gh$

$13.6g=gh$

$h=13.6cm$