Answer
The average blood pressure in a person's foot is $210~mm~Hg$
Work Step by Step
We can find the increase in blood pressure in the foot (compared with the aorta) due to the height difference with the aorta:
$\Delta P = \rho~g~h$
$\Delta P = (1050~kg/m^3)(9.80~m/s^2)(1.37~m)$
$\Delta P = 14097~N/m^2$
We can find the height $h$ of mercury that would have this difference in pressure:
$\rho~g~h = 14097~N/m^2$
$h = \frac{14097~N/m^2}{\rho~g}$
$h = \frac{14097~N/m^2}{(13,600~kg/m^3)(9.80~m/s^2)}$
$h = 0.106~m = 106~mm$
The average blood pressure in a person's foot is the pressure increase due to the height difference, added to the pressure at the aorta. We can find the average blood pressure in a person's foot:
$P_{ave} = P_{aorta}+ \Delta P$
$P_{ave} = (104~mm~Hg)+ (106~mm~Hg)$
$P_{ave} = 210~mm~Hg$
The average blood pressure in a person's foot is $210~mm~Hg$.
