Pressurized Cabins in Aircrafts

[Ron]

Can someone please tell me why do aircrafts have pressurized cabins? Has it got something to do with the difference between the low atmospheric pressure outside the aircrafts (since they fly at very high altitudes) & the pressure inside the aircraft?

 

Also if the same force is applied for the same time to a car & a loaded truck, which of the two will pick up greater speed & why?

 

Thanks,

 

Ron

[Mr Skeptic]

Airplanes fly at high altitude (I think for fuel economy) where the air is too thin for us to breathe. They only partially compress the cabins, which is why your ears pop. However, this increases the weight of the airplane, for example the pressurized cabin of a boeing 747 weighs an extra ton due to all that air.

 

The second of your questions is answered here: http://en.wikipedia.org/wiki/Newton%27s_laws

[Ophiolite]

The pressurisation is set to the equivalent of about 7,000'. If ground level air pressure were maintained it would place additional stresses on the aircraft.

[ewmon]

High altitude flying conserves fuel and helps avoid adverse weather/turbulence.

 

The pressurisation is set to the equivalent of about 7,000'. If ground level air pressure were maintained it would place additional stresses on the aircraft.

...and then there's the aircraft's maximum pressure differential between cabin and atmosphere that must not be exceeded, otherwise the hull might rupture.