## College Physics (4th Edition)

The average blood pressure in a person's foot is $210~mm~Hg$
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 $210~mm~Hg$.