Q128 / 180 · AIIMS 2006 · Physics
By sucking through a straw, a student can reduce the pressure in his lungs to $750 \mathrm{~mm}$ of $\mathrm{Hg}$ (density $=13.6 \mathrm{~g} / \mathrm{cm}^3$ ). Using the straw, he can drink water from a glass upto a maximum depth of
- A$10 \mathrm{~cm}$
- B$75 \mathrm{~cm}$
- Correct answerC$13.6 \mathrm{~cm}$
- D$1.36 \mathrm{~cm}$
Solution
Pressure difference between lungs and atmosphere $=760 \mathrm{~mm}-750 \mathrm{~mm}=10 \mathrm{~mm}=1 \mathrm{~cm}$ of $\mathrm{Hg}$.
Pressure difference $=1 \times 13.6 \times g=l \times 1 \times g$ of water
i.e., one can draw from a depth of $13.6 \mathrm{~cm}$ of water.
Hence, the correct answer is option: 'C'.