Final answer:
When measuring blood pressure at 0.500 m below the heart, we calculate the added pressure from the blood column and adjust the readings accordingly. The increase in pressure results in a new blood pressure reading of 128/84 mm Hg, corresponding to option C.
Step-by-step explanation:
When you measure a standing person's blood pressure with the cuff on their leg, which is 0.500 m below the heart, you must account for the additional pressure exerted by the height of the blood column above that point. To calculate this, we utilize the relationship P = hρg (pressure is equal to the height times the density of the liquid times the acceleration due to gravity). The density of mercury is 13.6 times the density of water, and since 1.0 mm Hg is equal to 133 Pa, we can find the pressure increase due to the blood column and convert it to mm Hg.
For the systolic blood pressure, we add the additional pressure to the original 120 mm Hg measured at the heart, and for the diastolic blood pressure, we add it to the 80 mm Hg. Without considering the fluid's resistance, the increase in pressure due to the weight of the blood alone will be approximately 0.500 m × 1050 kg/m^3 × 9.81 m/s^2 (density of blood is approximately 1050 kg/m^3). After calculating the pressure in pascals and converting it to mm Hg, we add this value to both systolic and diastolic pressures. After calculating the correct increase in pressure, we find that the new blood pressure readings at the leg level are 128/84 mm Hg, which corresponds to option C. Therefore, the answer to the question is C. 128/84 mm Hg.