Inertia on Planes: Pressure Differences Inside?

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Discussion Overview

The discussion revolves around the concept of inertia experienced on an airplane, particularly focusing on the effects of acceleration on air pressure inside the cabin. Participants explore how inertia influences both passengers and the air within the aircraft during acceleration and constant speed phases.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that during acceleration, passengers feel a force pushing them against their seats due to inertia, questioning the impact on air pressure inside the cabin.
  • Another participant claims that pressure decreases towards the front and rear of the cabin during acceleration, using the behavior of a helium balloon as an illustrative example.
  • A different viewpoint suggests that the sensation of being pushed against the seat is due to the plane pushing the seat into the passenger, describing this as a fictitious force similar to centrifugal force in a turning vehicle.
  • One participant posits that while air may experience slight compression during acceleration, this effect is negligible and short-lived, while also noting that pressure differences will stabilize once the plane reaches constant speed.
  • Another participant argues that air remains at the rear during acceleration but will experience pressure differences when the plane reaches constant speed, leading to diffusion and a near-constant pressure state when not accelerating rapidly.

Areas of Agreement / Disagreement

Participants express differing views on the effects of acceleration on air pressure and the nature of forces experienced by passengers. There is no consensus on the extent or significance of these effects, indicating multiple competing perspectives.

Contextual Notes

Some claims depend on assumptions about the behavior of air under acceleration, and there are unresolved questions regarding the magnitude of pressure changes and the duration of effects during different phases of flight.

Blacklukes
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Hello, I have a question regarding inertia. When we are on a plane, when it increases its speed we feel a force that goes on the opposite direction pushing us against the seat right? What about the air inside the plane, are there any difference in pressure due to inertia?
 
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Absolutely! The pressure decreases towards the front of the cabin & decreases towards the rear. You can observe the effect if you have a helium balloon on a string: When the aircraft accelerates, the balloon will drift towards the front of the cabin. You can see the same effect in an automobile. (Given that, which way will the balloon drift when an automobile makes a right turn?)
 
When you talk about you being "pushed against the seat", the plane is really pushing the seat into you. The moment the engines produce thrust, the plane (and by extension, the seat) is being accelerated forward and it's really pushing on you because you aren't moving due to your inertia. The sensation in the plane you are describing would a type of fictitious force, akin to feeling a "centrifugal force" inside of a car that's turn sharply.

I think the air would be compressed slightly when the plane is accelerating, but the compression would be negligible and only last for a very short amount of time.
 
At the moment, which you experience force which means acceleration, air would have stayed at the rear. However, when plane reaches constant speed air isgoing to experience pressure difference and net force, which means diffusion would happen. Thus pressure is almost constant when it is not accelerating so fast.
 

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