Question

What is the difference in blood pressure (mm-hg) between the bottom of the feet and the top of the head of a 1.87-m-tall person standing vertically? 1 mm-hg = 133 n/m2. the density of blood is 1050 kg/m3?

Answer 1

Using the hydraulic principle, hydraulic pressure is uniform in all directions of a static liquid, and increases with depth according to density.

Assuming the variation of blood pressure is the same as a static liquid, we need to find the difference according to height.

A column of 1.87 m of blood exerts a pressure of

1.87*1050 kg/m^3*9.81

= 19261 n/m^2 or 19261 Pa

Convert to mm-Hg

= 19261 n/m^2/ 133 (n/m^2/mm-Hg)

= 144.8 mm-Hg

= 145 mm-Hg (to three significant figures)