Final answer:
The lung pressure exerted by blowing into a manometer with a 70-cm difference in water column height is calculated as 6867 Pa using the density of water and the acceleration due to gravity.
Step-by-step explanation:
When a person blows into one side of a manometer and produces a 70-cm difference in the heights of the columns of water in the manometer arms, the pressure exerted by the lungs can be calculated using the height of the water column and the density of the fluid in the manometer. The pressure (P) exerted by the lungs is equal to the height difference (Δh) multiplied by the density (ρ) of the fluid (water in this case), and the acceleration due to gravity (g), which is P = ρ×g×Δh. Given that the density of water is 1000 kg/m³ and the acceleration due to gravity is approximately 9.81 m/s², the lung pressure can be calculated as follows:
P = 1000 kg/m³ × 9.81 m/s² × 0.70 m = 6867 Pa
This is the gauge pressure, which is the pressure relative to atmospheric pressure. If we wish to express this in other units such as mm Hg (torr) or in atmospheres, we can convert from pascals using the appropriate conversion factors.