Question

a. Why are commercial or any aircraft that fly at altitude, pressurized?

b. What is Pascal’s pressure assumption?

c. What are typical pressures used within commercial aircraft?

d. Explain air pressure and why it is higher at sea level than at high altitudes, support with diagrams if needed. (Hint, in a room is the cold air, it is at the floor. Is its density greater than hot air?)

Answer 1

a)

As we climb higher, air molecules are spread farther apart. When we breathe, our lungs take in less air, and less oxygen. Folks living in Denver, Colorado (5600 ft) are quite happy breathing the lower, 12 psi atmosphere. Climbing to a higher altitude, though, and the pressure drops really fast.

At 18,000 feet, the atmospheric pressure is down to 7.3 psi, about half the sea-level pressure. There just isn’t enough oxygen in a breath of air to adequately supply the brain. At this pressure, a healthy adult has only 20-30 minutes of useful consciousness.

Airliners fly between 30,000 and 43,000 feet. At those altitudes the atmosphere provides less than 4 psi of pressure. If you tried breathing at that altitude, your useful consciousness would be less than a minute (followed soon after by death).

To survive high altitudes, occupants of an aircraft need help breathing. The solution is to pump air into the airplane so the interior pressure is high enough to keep the humans comfortable.

B)

Pascal’s pressure assumption is fluid at rest no movement in fluid.

C)

Pressurization systems are designed to keep the interior cabin pressure between 12 and 11 psi at cruise altitude.

D)

Pressure is define as normal force exrerted on surface per unit area due random collision of air molecules (change in momentum).

pressure is higher at sea level than at high altitues because pressure depends up on the number of collision per unit time and velocity of air molecules were as number of collision depend up on the density of air due to gravitational force density of air is high near sea level as we go higher altitude density decreases. And velocity of air molecule is perpotional to the square root of absolute temperature as we go temperature goes on decreasing.