A simple barometer is constructed using a liquid Q1 of density 16.2g/cm³. Calculate the least length of the tube to be used to measure the pressure of 1.5atm. [Density of mercury = 13.6g/cm³, 1atm = 76.0 cm of Mercury]

A. 1358mm
B. 957mm
C. 760mm
D. 638mm

Correct Answer: Option D

D. 638mm

Explanation

Let hQ and ρQ be the least length and the density of Q1

while h and ρ are the length and density of mercury respectively.

h×ρ×g=hQ×ρQ×g

76cm×13.6×10=hQ×16.2×10

hQ=76×13.6×10/16.2×10

hQ=10336/162

hQ≊63.8cm=638mm