Question

(a) Convert normal blood pressure readings of 120 over 80 mm Hg to newtons per meter squared using the relationship for pressure due to the weight of a fluid (p=hrhog) rather than a conversion factor. (b) Explain why the blood pressure of an infant would likely be smaller than that of an adult. Specifically, consider the smaller height to which blood must be pumped.

(a) 3.58×10^4 N/m²
(b) Infants have smaller blood vessels.
(c) Infants have a higher heart rate.
(d) Infants have lower blood volume.

Answer 1

To convert blood pressure from mm Hg to N/m², use the formula P = hρg and the density of mercury. The blood pressure of an infant is smaller because their blood vessels are smaller and the height to which blood must be pumped is also smaller.

Step-by-step explanation:

To convert blood pressure readings from millimeters of mercury (mm Hg) to newtons per meter squared (N/m²), we can use the relationship for pressure due to the weight of a fluid, given by P = hρg.

Here, P represents the pressure, h is the height of the fluid column, ρ is the density of the fluid, and g is the acceleration due to gravity. In this case, we'll assume ρ = 13,600 kg/m³ for the density of mercury used in a manometer.

To convert 120 mm Hg to N/m², we multiply by the conversion factor 133 Pa/mm Hg and then by the density of mercury:

P = (120 mm Hg) × (133 Pa/mm Hg) × (13,600 kg/m³)

P = 3.58 × 10^4 N/m²

(b) The blood pressure of an infant is likely to be smaller than that of an adult because an infant's blood vessels are smaller and the height to which blood must be pumped is also smaller. This means that the pressure exerted on the blood vessels is lower, resulting in a smaller blood pressure.