Deriving Flight from First Principles. A random thought experiment

Before i get into this let me bore you a bit in this next paragraph. You may skip right ahead. Actually you may just read the next paragraph and skip the whole blog.

Disclaimer : This is still possibly wrong and incomplete, but it was a fun experiment in my head, and something i like doing when I am bored, which is trying to figure out how the great minds may have approached arriving at certain theories from what they know. I use the words “first principles” rather loosely here, to describe, “what we know at the moment”, or a basic theory that could lead us to more interesting slightly less obvious outcomes.

*Its currently unorganized unless you have some context on what Bernoullis principle is/how flight works and what pressure vs velocity relations are for fluids*

Principle : Derive the idea of flight from first principles.

Things I assume i know :

  1. Newton’s laws
  2. I need to create some sort of negative pressure on top so that my object will move up

Process conditions:

  1. Sitting in the car driving to work with my roomate, no access to google. Just regular San Diego traffic.


  1. Because I assumed that i would need to arrive at pressure differential between the top and bottom of a flying object/a plane (a flat 2D object, for simplification, no pun intended), i had to define the concept of pressure more clearly
  2. The concept of pressure for solids is rather straight forward, and i assumed it to be the force you can apply with that object on a unit area of any other body/ a surface, and here the force can be you pressing it down using ur muscle strength/just the sheer mass of the object. It took me some time to visualize the latter part because in my head i was just imagining me pushing down a spike on a piece of ground. However, once i arrived at the latter, i came upon point 4.
  3. I started focusing on the definition of a fluid here. At this juncture i was really going into a tizzy with imagining molecules randomly bumping into each other and moving a lot freer than a solid object because solid objects maintain their relative molecular configuration spatially, atleast a lot better than fluids which just move about a lot more in the same space. I started to then think about integrating the total effect pressure a fluid that is more chaotic vs a solid object would have on the same unit area. However, that didnt lead me anywhere because i missed one key point
  4. At this point my roomie (who was driving and not remotely interested in really thinking bout this as much as I was, and in an attempt to humoring me may be,,, ) butted in and was like, “Dude what about compressing an object isnt that another way of looking at pressure?”. Something at this point went off and started to get me thinking about mass.
  5. I started to — Imagine a molecule that is being suspended and has no velocity, and is at rest. This molecule would simply fall down due to gravity, and accelerate towards a surface, hence exert some weight on this surface. At this point i was still imagining something like a small lead ball landing on a surface and transferring some force to that point, effectively, some form of pressure. Now, i started to give that ball some velocity. The ball is still as heavy, but now that it has a horizontal velocity, the weight registered in the vertical down direction i imagined would be lesser since it has something that pushed it to the side. This was not a solid hypothesis, since that object would still be as heavy, and i dont think the downward force/the weight registered would essentially change since the vertical component / acceleration due to gravity here would still be the same.
  6. But, then again, a particle that is being accelerated / moved sideways now moves less downways (prototyping language), and hence its movement downwards/ the component is now less per unit time, and hence its possible to hypothesize that its acceleration is less in the downward direction.
  7. Force is change in momentum, and hence a particle that has a momentum m.v where the vertical component in which v changes is lesser than the horizontal, it can be concluded that the force, and hence pressure it applies on an object under it is lesser, when its in motion. Hence, a moving stream of particles with a horizontal velocity v is probably applying less pressure than a stream of particles that have a velocity v’ which is lesser.
  8. Hence the pressure differential/ the Bernoulli principle.

And phew, hence you can make things fly.





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Sreekanth N

Sreekanth N

Master of Prosoddity

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