Question

By sucking through a straw, a student can reduce the pressure in his lungs to 750 mm of Hg (density = 13.6 (gm / cm2)) using the straw, he can drink water from a glass up to a maximum depth of

(A) 10 cm

(B) 75 cm

(C) 13.6 cm

(D) 1.36 cm

Answer 1

Correct option: (C) 13.6 cm

Explanation:

Pressure difference between lungs of students &

Atmosphere = (760 – 750 mm of Hg

∴ P = 10 mm of Hg = 1 cm of Hg

i.e. hρg = 1 cm of Hg

For mercury, 1 cm of Hg = 1 cm × 13.6 × g ------- (P = hρg) & ρ = 13.6 (gm / cm3)

For mercury, Y cm of water = Y cm × 1 × g ------- ρ = 1 for water

Both should be equal

∴ 1 cm × 13.6 × g = Y cm × 1 × g

∴ Y = 13.6 cm

i.e. He can drink upto depth of 13.6 cm