## Arnab_Chatterjee 3 years ago Any questions on Aircrafts, Spacecrafts , Aeronautics & Astronautics people?

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1. mathavraj

hi again....well can you explain the future of todays commercial planes

2. wasu

no

3. quarkine

hey this is perhaps more of a aerodynamics question but since it seems related to the above topics i thought i may ask.can u help with this - we know that a spherical ball falling in a fluid is acted by viscous force calculated by stoke's law... but how to calculate the viscous force on and terminal velocity of a square sheet falling/moving in a fluid medium for instance say a square sheet of iron ( or something dense) is falling inside sea from a ship such that its flat surface is parallel to sea surface?

4. ghazi

when a plane flies at at altitude of 15000 feet from where does it get upthrust? Due to the upthrust it takes off but what about the upthrust when it is flying high?

5. Arnab_Chatterjee

Well @ghazi , The upthrust that you are talking about is generated always when the aircraft is in motion (accelerated by its props, jets), so you get upthrust when you are taking off as well as when you are at 15000 ft... the only thing that if the airplane is at the same velocity as when it was taking of,f at15000 ft ...then the lift or the upthrust generated by its wings will be considerably lesser because the air at high altitudes is much less dense (viscosity). Hope this is it... @Arnab_Chatterjee Check the diagram attached.

6. ghazi

well the diagram that you've attache is the time when airplane lifts off..what about the conditions when it is at a certain altitude ....from where does it get upthrust..wings just provides direction...these ain't wings of bird which is in motion to give upthrust...so kindly explain me if it's okay..thank you

7. Arnab_Chatterjee

Its okay...now from the diagram you see, that when the aircraft is in motion, air flows over both over and under the wing....The aircraft's wing is called an aerofoil.. Now...to be simple you can see, by the unique design of the airfoil lets the air passing over it to let go easily without much obstruction...while it is just the opposite for the case of the air flowing below the wing....Thus by Bernoulli's Equation, air (actually any fluid) wants to move from a region of a higher pressure to a region of lower pressure ...so same is the thing here....and thus the air flowing below the wing pushes the wing upward as it wants to go to the region of lower pressure, which lifts the airplane......... In case you don't know Bernoulli's Equation, think about the flow of wind on earth and formation of storms where wind again moves from a region of higher pressure (barometric) to a region of low pressure.. :)

8. ghazi

well this theory is a basic understanding but recently at cambridge university this theory has been stated as obsolete and i am afraid the thing that you've explained is bit contradictory..and i would say not self satisfactory ...by the way the video of new research is on youtube you can find more over there

9. Arnab_Chatterjee

Yes.... I know this is actually got quite contradictions....but still the age old popular explanation choice.....they are using laminar flow...

10. ghazi

that's why i asked... by the way thanks for giving your time