Thank you so much (I already own curiosity though, lol)

6:05 I understand your explanation of the what creates the lift force (i.e. a pressure difference due to velocity difference, according to Bernoulli's Principle) but then... 6:30 I don't see why the fluid flow being "pinched" above the leading edge of the wing results in LOWER density/pressure? Instead, I'd expect this constriction of air molecules to cause HIGHER pressure? 6:42 I also don't see the connection with "Conservation of Mass" which you state, but don't explain. 7:08 Again, you state what the flow would look like without circulation but you don't explain why.

Conservation of mass means that for the same amount of fluid to flow through the constricted section, it's velocity must increase. And Bernoulli's equation tells us that an increase in velocity is accompanied by a reduction in pressure (conservation of energy).

@@TheEfficientEngineer Thanks for replying with an explanation, which helped me understand how Conservation of Mass applies. I also watched another video explaining how wings create lift (by the channel Sixty Symbols) which I found helpful. How circulation is relevant in this case remains a mystery...

@@GonzoTehGreat It's best to think of the air as a fluid. Also whatever the reason, it is the difference in pressure between the top and bottom of the wing that does most of the work. The various reasons, Bernoulli, Coanda or Newton, will have varying input depending on speed and angle of attack. Flaps only work at low speeds. At cruising speed they just add drag. Same with angle of attack. It took until computers became powerful enough to do the calculations for some of this to be unravelled, so its no wonder that it is still being argued about! Edited for spelling.

I’m going to shamelessly steal this pun

Just the third one 😄

It also stresses laymen like me. I know that wings create lift. I still don’t understand why, though sometimes I think I do

Nobody understands why. That’s why it’s called the theory of lift. Even super computers only get close to quantifying it. We only know what conditions need to be satisfied to create it, not the why.

@@Bartonovich52 Oh, I am glad to hear that! I thought it might be a shortage of understanding on my part. So, in essence, we have a description or the ‘what’ of this phenomenon, not the ‘how’ or ‘why.’ Thanks

Really? I thought we have proved that the lift is caused by the Coanda effect not the Bernoulli effect.

@@jackz1620 Coanda is just a small part that allows the boundary layer not to detach from the airfoil and produces a bit percentage of the lift with the downwash but lift is based mainly in pressure differencial by bernouilli effect

pitty it is not based on physics for all the benoulli version. See my comments above.

@@jackz1620 ​ @Ignacio Trueba Coanda does not happen above an airfoil. It is a jet or sheet of air, FORCED into an otherwise still air environment. There is continual entrainment. There is neither of those above an airfoil. . Using the "Bernoulli Effect" as commonly done is an equally incorrect way of explaining lift. *Understanding Lift Correctly:* rxesywwbdscllwpn.quora.com/

Totally agree!

Would you comment, or LIKE if appropriate, this short piece of the story for the layman? My 11 yo granddaughter did all the editing. *ukposts.info/have/v-deo/a32EpZilmYF1zoE.html*

It's not totally correct

@@baloog8 yeah, I agree, I started to learn fluid mechanical to understand exactly how this aerodynamics works, because I learned solid mechanical approach, so it's a little different when you can think a solid as fluid with an extremely high viscosity.

Lift is action and reaction. The action is the deflection of air molecules downwards, the reaction is the wing being pushed upwards. Pressure differences are secondary. If there is no downflow of air from the wing, there is no lift. R

Life is not totally correct, but we can enjoy it.@@baloog8

Absolutely insane how I’m in the last 2 weeks of fluid mechanics and we’re doing external flow now, and this guy uploads precisely on lift 😂

be careful, physics and engineering are two different things! Still no one is certain on how an airplane flies!

@@rogerdodger8813 I would say people are certain on how airplanes fly, just lacking in certainty regarding deeper issues relating to CFD.

@@rogerdodger8813 That information has the value of zero.

Watch large jets taking off or landing in the rain sometime. You can sometimes catch a glimpse that the air and water spray over the top surface is moving substantially faster than the jet is even travelling down the runway, and the air is actually accelerating over the wing, past the flaps and then downward.

The explanation with potential flows (uniform+circulatory) is actually more practical as they are used in many preliminary design tools like xflr,xfoil etc

Yes. The textbooks approach the problem in a piecemeal yet detailed fashion. And in the end, you are either completely confused, or the lightbulb goes off in your head. What is funny about the Kutta condition and Circulation is that you can see these first hand by doing an almost childlike experiment in the bathtub with a model airplane wing , and pepper sprinkled on the surface of the water. In effect a 2D wind tunnel, where you move the wing through it instead of the water moving. The pepper particles show the startup vortex off the trailing edge of the wing (Kutta Condition), and when you move the wing from right to left through the water then suddenly remove it, you see a ghostly slow clockwise motion (Circulation) of the area where you removed the wing. Got this little experiment from a book called Aerodynamics for Engineers. So I guess its college level.😜

good video with wrong explanation

Glad to hear it - thank you!

Thanks. :) Agreed, circulation is often not discussed which is a shame!

hey man, uni student here and im always confused abt what circulation is. yes , there is a mathematical definition abt it but what is the physical meaning on it?

at 3:53, the secret to lift is Persistent zones of PRESSURE difference.!!!. not circulation

@ David Davids Pressure difference would not exist without circulation. A tiny spoiler on top of the wing is very good at stopping circulation and instantly destroying lift.

@ ileonlite Circulation is what you are left with after you subtract the free steam vectors from the airflow around a wing.

no, it's not.

Yes, it is @@SoloRenegade

Keep looking, there are far better and more accurate explanations of lift on UKposts. This video is full of misconceptions and inaccuracies.

no, it's not.

there is far better on youtube, and that are actually correct, unlike this video.

same here

Lift is action and reaction. The action is the deflection of air molecules downwards, the reaction is the wing being pushed upwards. Pressure differences are secondary. If there is no downflow of air from the wing, there is no lift. R

⁠@@RalphEllisto get to the action ur describing is through out the differential pressure caused by the airfoil. With no action there’s no reaction 3rd newtons law 😂

no it's not.

And also mentioning Newton's law too. A big plus there

wrong. 1) lift occurs BENEATH a wing. 2) a major Source of lift is the presence of a Persistent Zone of Reduced pressure (eg, a specific pattern of TURBULENCE.) ABOVE a wing. 3) not circulation

@ David davids Wrong. The lower surface of the wing not only has almost nothing to do with lift creation... but there is actually low pressure under most wings. The only wings that create high pressure underneath them are supercritical airfoils which still need the low pressure on the upper surface for a lot of the lift and most lift at higher angles of attack and lift coefficients... and the few fighter aircraft that can do high alpha maneuvers at which point the drag coefficient is about ten times as high as it would be to create the same lift coefficient in at a lower angle of attack. If your theory is true, explain how a tiny spoiler or a layer of hoar frost on top of a wing can be so effective at destroying lift.

@@Bartonovich52 'there is actually low pressure under most wings' ????? jeezuss. that massively incorrect statement tells us all that, we can IGNORE anything else that you might say. out

@@daviddavids2884 I am not sure whether you couldn't comprehend whatever is depicted in the video or just needlessly trying to be a moron by just completely ignoring what is being explained. 1) True , there is lift below the wing.2) True, the cause of the lift is presence of reduced air pressure above the wing.3) But the video addresses why is there such a pressure distribution...that is a level deeper in explaining the cause of lift than what you know or think...that specific pressure distribution is in part attributed to a mathematical equivalency of circulation

Hey nigga

While technically true, it's not uncommon to refer to the "suction side" and the "pressure side" of an airfoil, and it's fine to think of them that way in the context of gauge pressure. Sure, the reality is a reduced inwards pressure, but mathematically and even conceptually, it works just fine either way.

Nice! and just to add a little: Higher pitch attitude on landing also increases landing run on nose wheeled aircraft as the maximum application of brakes requires the nose wheel to be on the ground. This nose lowering time is limited by the aircraft structure. Thus in the case of flap failures it is often the case that the use of slats is limited to some intermediate position.

Yes but that is annoying and incompressible flow is so pretty!

No, it would not remain unchanged. With significant flow separation at the trailing edge the Kutta condition no longer holds, which leads to a great reduction (and sometimes even total reduction) in circulation. Circulation is the cause of acceleration on the top surface. Less circulation -> less acceleration -> less reduction in pressure on top (Bernoulli) -> less lift. It is not Newton or Bernoulli, it is both, and by exactly the same amount. They are equivalent. Two sides of the same coin.

flat piece of plywood produces the same lift when tilted.. so youve proved nothing..sorry..dr johnny

But why does the faster velocity occur? And why is air deflected downwards? A faster velocity on top and slower on bottom is the definition of having circulation

Thank you

The propeller blades are clearly curved as to incline the airflow backwards, the direction the trailling edge is pointing is something a 2 year old would realize so I'm not gonna spare you for that, and they do essentially the same thing, low pressure area in front of the blade. And wingtip vortexes don't travel downwards, wtf, you can see planes flying through smoke, the votexes grow bigger over time, but they stay in the same general area. I am only finding it now that there's the equivalent of Flat-Earthers for fluid dynamics, I thought it was too smart of a field for you guys to bother.

what if both theories are applied at the same time

Bernoulli is just a rewrite/application of Newton. Look at how the Bernoulli principle is derived if you don't believe me.

Finally, someone who knows lift has nothing to do with Bernoulli and everything to do with Newton.

@@P13586 For the life of me I don't see why this is so difficult to understand.

You are talking about the 3rd law by the way. Anyway, you are partially correct, Newton's downwash is one reason, pressure difference is another though. You need both on planes like a 747. But no sane person is arguing about that. The only thing that is hard to explain is why the air travels faster at the top. Everything else is trivial.

Nope it is not. Another non-physical explanation . Nothing said about origin of FORCE. Not Energy conservation and not 3d law of Newton can explain FORCE

@@AndrewPa do you have a link to a description or a description of your own?

Unfortunately, you have been mislead. As I previously posted: . It's rather disappointing to see, while this engineer have good intentions, He uses poor wording in several places. . I see the following problems here. . The graph at the left at 4:14 shows the change from ambient, or gage pressures. Saying that pressure above “is greater”, as you do, is misleading and confusing. . It is more correct to say that the *change or difference from ambient* is larger above. You do refer to it as "suction pressure" which sort of says it, but we must remember that you don't actually suck or pull on a fluid, but suction is an accepted term short for “lowering the pressure so a higher pressure can push toward it." .. Unfortunately, he also repeats the big fallacy at 6:15, that the "increase in air velocity creates an area of lower pressure." This directly violates Newton’s Laws. Acceleration does not cause a force. Force causes acceleration. He also states the equally incorrect converse about the lower air "decrease in velocity creates a higher pressure." It is exactly the opposite. Air has mass and a force is required to accelerate any mass. It is a pressure difference that provides this accelerating force to slow it. . The fact that the velocity increase is accompanied by the pressure decrease (and visa-versa) IS CONSISTENT WITH Bernoulli's Principle. However, Bernoulli's Principle DOES NOT assign a cause and effect! It only says that a pressure changes and velocity changes *accompany each other.* . In the mid 1700s it was Euler, following up on Bernoulli's work, that determined that it is a Pressure Gradient that Accelerates fluid. This is Newton's Laws operating in fluids. When there is a pressure difference between two locations, the higher pressure pushes more and accelerates the fluid toward the lower pressure. This is simple and intuitive IF you understand what Newton was supposed to teach you. . Pressures are the cause! . At least he correctly states that the top/bottom pressure difference _is_ the lift. . Then, using Kutta as the cause is equally poor. It still does not explain what the force is accelerating (or decelerating) the air above (below). Kutta is something that had to be added because the initial mathematical calculations failed to correctly model the actual flow - to correct the math, not to make the flow correct. . The circulation story is also backwards. Yes, we can *deconstruct" the flow into two components; one unidirectional and one circulating. BUT what is it precisely that causes this circulation? This story says it is because the air can't make that turn around the trailing edge, but this still does NOT explain the force causing the accelerations we see. We can directly observe the air NOT curving backwards around the trailing edge. Why would it want to do this swirl-around stunt? . As @icojb25 explains so well in another comment: “In terms of the circulation, I guess one needs to understand "circulation" is actually a mathematical concept (ie not real) - used by physicists and engineers in the 1920's when trying to come up with the first aerodynamic theories (like thin airfoil, LLT etc). So remember, there is no magical vorticity "circulating" around the airfoil generating lift. Its a very elegant concept though, and great for many simpler explanations. One just has to decide if you want to explain a physical phenomenon using a non-physical (abstract) concept like circulation, however elegant.” . The pinching above is not just "incomplete", but completely false idea because there is no wall further above ...AND...AND there is another “Pinch Point" right below the wing (time 6:43), where it is "pinched" from above by the wing bottom BUT with NO speed increase, nor pressure reduction!! In fact, the pressure is higher and flow slower.!.!.!. Therefore, serious problem with "pinching". BAD SCIENCE. . Yes, That "Newton Action / Reaction" thing does occur! It must! However, it is the (net) pressure that pushes up on the wing (AS you correctly state with the pressure difference talk) BUT those VERY SAME pressures also cause ALL accelerations of air around the wing. . Bottom line: Once you understand the most fundamental principle, that cannot be violated that: Pressure Gradients CAUSE Acceleration, then everything is easily explained -- cause and effect included.!. See *Understanding Lift Correctly:*. ***rxesywwbdscllwpn.quora.com/*

@@Observ45er I read your previous post, and have responded directly to it, as it is riddled with errors.

@@XPLAlN I'll stay in the other thread to avoid confusion and have answered there.

@adb012 I'd like your further comments. I have an ulterior motive... As an engineer, I appreciate this is complex and, therefore language is very important. Since I'm critical of words, I'll be very careful with mine... . Example: . What gets me is that while he carefully states Bernoulli's Principle well, at 6:15 he actually says "the increase in air velocity above the airfoil creates an area of lower pressure." [above wing] . A velocity increase is acceleration. It would have been better had he said "the *increased* velocity" or just "speed" it would be accurate. . It isn't the acceleration that causes the transverse gradient, but rather the speed along the curve. . Yes, of course there are tangential speed changes as well along that curved flow, but the transverse gradient is from the air's natural tendency to continue straight. It is the "stretching/swinging/flinging away from the curve's center - what some people consider the inertial force". I think it should be called the centrifugal effect (not force). This is the idea that you feel pulled outward traveling around a curve. Previously called 'centrifugal' force. . Here, we actually do have the case where speed (in the curved flow) actually can be said to "cause" a pressure change. . It causes the *transverse* gradient rather than the more common longitudinal (proverse or adverse) gradient that changes speed. I say that is an unfortunate choice of words in a very technical subject where there are so many misconceptions being spread all the time by so many well meaning amateur scientists. ... .. .. So... My motive is for your comments on this short, simplified video explanation of what I just mentioned. Because my 11 yo granddaughter did the video editing, I would appreciate if you would consider a LIKEit if you feel it appropriate. You should also check my UKposts About. I'd prefer your comment under the video as threads can get long. *ukposts.info/have/v-deo/a32EpZilmYF1zoE.html* . Regards

​@@Observ45er ... I am going to reply to you here since you posted this comment here, and then I am going to copy this reply in your video. The effect that you describe is correct. A parcel of air has to obey Newton's 2nd law (and the others too, of course) that says that F=m*a. The parcel of air has a mass (even if it is a differential mass) so, to be subject to an acceleration, it needs to be subject to a net force (even if it is a differential force). So if the parcel is accelerated, then there must be net force acting on it and, if we neglect viscous drag (say that we are outside the boundary layer), then we are left with pressure only, so an accelerated parcel of air means a pressure gradient. This applies both in the tangential and normal (centripetal) directions. In the tangential direction, the acceleration causes a change in the magnitude of the speed vector of the parcel of air (i.e. the parcel of air will increase or decrease the speed), while in the normal direction it causes a change in the direction of the speed vector. Now, you focus exclusively in the normal direction. Again, that effect exists and your explanation of the effect itself is correct, except that it can't by itself explain the cause of lift. I will start by admitting that I don't remember everything I learnt (and used to teach) about lift. Bute here you have several points to consider: - Why does a flat airfoil (like a piece of balsa board) generate lift, and no only that, but it generates as much lift as any other airfoil at the same incremental angle of attack above the zero-lift angle of attack? (as long as it doesn't stall, which the balsa board will do at a lower angle of attack than a conventional airfoil) - How does a conventional asymmetrical airfoil manage to produce lift when flying upside-down? And why does that hold true even when it is a thin cambered airfoil (one where what would be the upper surface is convex and the lower surface is concave, except that it is upside down so you have the concave side up and the convex side down). - Consider the following 2D Venturi tube. You have 2 lateral walls that parallel are very far away to each other (say 200 meters away). You have a bottom and a top that start parallel to each other with an internal height of 1 meter. Air flows along that tube of rectangular section (1m x 200 m). At some point, the starts a straight ramp up at a shallow angle, at the same point, the top also starts a down slope of the same shallow angle. The lateral walls remain at constant distance to each other. In this way, the section starts to constrict, from 1m x 200m, to 0.8m x 200m, to 0.6m x 200m and so on, in a constant and symmetrical ramp in the top and bottom. Due to continuity (conservation of mass), the flow will gradually accelerate along this upstream side of the venturi, and as it does so, the pressure will go down. Several meters down this double ramp, at the point where the top and bottom are 0.1m away, the flow will be moving 10 times faster and, BY Bernoulli (note I didn't seay BECAUSE of..., that was intentional), the pressure will be much much lower. So you have a constant and gradual decrease in pressure from the point where the constriction started down to this point, yet all the parcels of flow where moving in straight lines. Conclusion? You can (and DO) have changes in pressure even if the flow is moving in a straight line. - I remember there was a "thin airfoils" approximation used to estimate how an airfoil would behave (lift vs angle of attack) that totally neglected the vertical acceleration of the flow, and it was quite accurate for airfoils up to 10 or 12% of thickness at cruise-like angles of attack. - This one is the most crucial one for me: Have you though why the flow NEEDS to curve and follow the airfoil? Typical answer to that question is "because if not it would leave a vacuum behind and that would pull the flow back to the airfoil". That is wrong. You could have a recirculating bubble, like you have at higher angles of attack in a stall. Saying ""the cause of the transverse pressure gradient is that the airflow turns" is more a "political position" that an accurate scientific statement. We could as well say that the cause why the airflow turns is that i flows through a transverse pressure gradient, and in a classical Newtonian view it would be more reasonable to say so: We typically say that a force causes an acceleration, not the other way around. Whether that classical Newtonian view is fair is a different question, I tend to think it is not, that force and acceleration are concurrent and 2 parts of the same phenomena, not one the cause of the other. Let me give you an example. You have a train taking a turn. The lateral normal force between the rails and the flange of the wheel provides the centripetal force that changes the train's direction. How doe the rail know to apply the exact force necessary for the train to keep that exact curve at that speed? The force causes the train to turn or the train turning causes the force? Well, in fluid dynamics it is like this, but worse. Everything is correlated, concurrent, and integrating with everything. You have a pressure field and a velocity field (and a viscos stress field too) and a vorticity field all "conspiring" together to create a solution that meet the 2 boundary conditions: The boundary of the airfoil shall not be penetrated and the flow will separate at the trailing edge. Saying that one thing causes the other is, in my opinion, not real. - Finally, at the end of the day conservation of momentum (or variation of momentum in the presence of a force) does apply. If the air is pushing the wing up, then the wing must be pushing the air down/ That means that the air has to bend its direction from say horizontal far away upstream of the wing to diagonal horizontal and down far away downstream. The turning that you described is PART of this phenomena, but not the that air changes direction long before it reaches the wing, keeps changing direction long after it already passed the wing, and also quite far away above and below the wing. Lift is truly a very complicated phenomena. Any simplistic explanation has to be either wrong or incomplete. Yours in correct but uncomplete.

@@adb012 .. For readability, UKposts accepts ENTER for paragraphs. You can paste paragraph marks into Quora from another document such as a Word doc. I compose in Word then Paste. Double marks with a period between works better.. .. In your order… .. First, you think you have a gotcha, but you haven’t. This is not a subject I embarked upon within the last few weeks. Read my About for my UKposts account. .. You repeat what I summarize in the video, Newton’s #1: “Acceleration requires a force.” .. The video title and the description below it clearly say that the video is about the upper pressure reduction and ONLY the upper pressure reduction. The primary goal is to refute all the common misconceptions in so many amateur videos and papers that claim things like the venturi effect (pinching) and a misunderstanding of Bernoulli’s Principle and Equation. .. .. This ‘around the bend, over the top’ explanation covers all the wing types you mention; flat; symmetric; cambered; normal and inverted ‘thin’ camber (Wright’s); boat sail and keel. It also figures into the Coanda Effect, Magnus Effect and Fletner wing as well as the self-centering ball on a column of air (not the Bernoulli nonsense so often claimed). .. I note that the very similar flow around a flat wing at 5 degrees AoA is shown in: Introduction to John D. Anderson Fund of aero 5th Edition. Flat plate flow Figure 4.52 Page 391. .. .. Note that in my first airflow diagram I have a semicircle. The key point that needs understanding is that it is the flow path/shape that it significant, NOT simply the surface shape. All the ‘normal’ wings have this same phenomenon above them - curved flow affected by the same “inertial force” (as some folks like to call it these days). On ALL these wings, the air goes around that upper bend, one way or another - Bending or turning the air…. .. .. .. .. .. RE: Gradual venturi. That is a longitudinal Pressure Gradient; along the flow. .. The one formed by the curved flow, the main topic in my video, is transverse; across the existing flow. You seem to be implying that having the transverse Pressure Gradient somehow negates the possibility of a longitudinal one and I see no such logic. .. In fact, above the wing from the LE stagnation line back, there is both longitudinal and transverse Pressure Gradients. .. So, I don’t see any problem it introduces. .. .. Pressure Gradient across a flow that curves it. .. This is where Boeing’s Doug McLean likes to say that it is a two way street. A transverse Pressure Gradient that is there before the flow moves is enhanced by the moving flow’s curved path. The two-way path is not simply both ways because the reverse path you have the surface providing the boundary condition that mandates the curved flow. .. In addition, that the air would ‘go straight’ has two conditions and I challenge you to examine both the moving air (wind tunnel) frames and the moving wing (flying) reference frames. These two cases have different values of momentum. .. I also point out that viewing a wing flying by shows what seems to contradict this common misunderstanding that says that faster air has a lower pressure. With the flying wing, still air frame-of-reference, the upper air actually has a slower speed than the lower air, but it has completely reversed direction; a high acceleration caused by the mostly longitudinal Gradient. This is real data from a lift generating wing shows this and all fundamental principles apply. .. I don’t understand the intent of that “thin airfoil - ignore the vertical”. All I can think is that if you can calculate the surface pressures, ignoring momentum transfer, you have the lift. In fact a paper by Charles Eastlake describes just that. He described how lift can be CALCULATED by either of two methods. 1) Surface pressure calculation using as I recall Bernoulli and. 2) Momentum change of surrounding air. I spoke with him about it. .. wiki.mattrude.com/images/4/44/Bernoulli_Newton_Lift.pdf .. Re: The NEED to turn and ‘vacuum’. The flat plate flow in Anderson shows that ‘bubble’ above the LE allowing a flow virtually identical to the common asymmetrical cambered wing. This easily reinforces the concept that we need to focus on the flow, not simply the detailed shape. The flows are ALL similar and are compatible with the video’s description. .. Yes you can say that the curve is caused by the transverse gradient, but the flow then clearly enhances that gradient. If we set up the initial gradient, then start the flow, that gradient is increase with the speed of the flow due to the inertia effect. You can’t maintain the original Gradient once the flow moves without changing mass and that it off the table, right?. .. I don’t consider that Political. .. The curved flow clearly enhances the transverse Gradient. This situation is clearly NOT one of simple speed causing a gradient. A pressure Gradient causes a linear, or tangential acceleration, but a curved speed causes a transverse Gradient. This is not a simple bidirectional A< - > B thing. It is not simply reversed in both directions. .. The transverse Gradient is indeed something that sounds like the Bernoulli misconception of speed causing a pressure reduction; Just not like so many characterize it as a longitudinal gradient. This causes a gradient across the flow, not downstream pressure reduction. The problem here is that they are orthogonal gradients in play. This is where McLean says that one “supports” the other rather than “causes” it and I think that is fair. .. I don’t know if that comes across well in text like this. .. RE Train: First, the flange does not come into play on a train curve. Rail wheels are conical (cones) because they are on a solid shaft and need to cover different distances around the curve. .. “lateral normal” is an oxymoron, but I think I know what you mean, just lateral. .. Regardless we can use an auto on a curve just as well for what I think you are getting at. .. You are on acceleration and Newton’s Third Law. What is the cause of the two forces ? Is it the “action”? Or is it the “reaction” that causes things to happen. By the way, this (radial acceleration commonly called centripetal) is no different from linear acceleration. Whether you speed up, slow down or curve, it is acceleration. We must still have the action and reaction to satisfy Newton-3. .. The train’s motion / inertia is the cause and I maintain that these are NOT two separate and distinct forces as implied by Newton’s original wording. Rather there are two “parts” to a force. A force, ALL forces act in two opposite directions at once. There is no unidirectional force. That is a long-standing illusion imprinted in our brains by that original wording. .. It is the same if we are skateboards and I push you, it is my arm muscles that apply an outward force between us, pushing us away from each other. One force, two “parts”, two moving objects. .. Likewise, taking this high level view with a wing, the pressure pushes both up on the wing and own on some air --- Newton is happy and other things happen - covered elsewhere… Because: Again, my explanation is NOT EXPLAINING LIFT and does NOT claim to be. It is a ONE MINUTE explanation of ONE difficult aspect of lift. BTW: it also ignores up-wash, down-wash, speed variations, below wing phenomenon and tip-spill. .. Regards

I am from India but now in Canada. Have you mastered the concept of potential vortices, if so we can discuss