a pilot records the atmospheric pressure outside his plane as 63cm of Hg while a ground observer records a reading of 75cm of Hg with his barometer. Assuming that the density of air is constant, calculate the height of the plane above the ground. (take the relative densities of air and mecury as 0.00136 and 13.6 respectively)
A. 120m B. 138m C. 274m D. 1200m E. 120,000m
Correct Answer: D
Explanation
pressure change for air = pressure change for mercury hpg = Hpg h x 0.00136 x g = (75 - 63) x 13.6 x g h = \(\frac{12 \times 13.6}{0.00136}\) = 120,000cm = 1,200m
