# Bernoulli's principle **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [November 7, 2004, 4:32am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459 "2004-11-07T04:32:48Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 12, 2004, 4:26am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/21 "2004-11-12T04:26:05Z")
> [@Chronos](#): > > Of course, another way to fly inverted, for any plane, is to just start off with enough altitude, and just lose altitude while you’re inverted. But note that in unaccelerated flight (e.g. descending at a constant rate) the wing must produce the same lift that it would in level flight. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 12, 2004, 4:32am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/22 "2004-11-12T04:32:09Z")
> [@Plynck](#): > > How can planes fly upside down? This is the classic question that confounds the Bernoulli-only explanation. If lift depends solely on the shape of the wing, there should be no way to support an aircraft when the curved surface is down and the flat one is up. But planes with wings like that fly inverted every day. So there must be something Newtonian at work. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 12, 2004, 11:22am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/23 "2004-11-12T11:22:31Z")
> [@rwjefferson](#): > > Where does [Bernoulli](http://theory.uwinnipeg.ca/mod_tech/node68.html) fit in? Bernoulli’s formula is actually a derivative of Newton’s F=MA. It applies ONLY to fluids flowing parallel to a surface. Bernoulli does not address fluids changing direction. Pressure involves matter changing direction > [@](#): > > If you remember derivatives from your Calculus class, you know that Newton also gets credit for Calculus. Bernoulli is but a Vector of Newton. A Vector of Newton? > [@Xema](#): > > So there must be something Newtonian at work. it’s all newtonian–even bernoulli is newtonian 🙂 ---
**Author:** ![rwjefferson](https://avatars.discourse-cdn.com/v4/letter/r/a6a055/32.png) [@rwjefferson](https://boards.straightdope.com/u/rwjefferson)\ **Post date:** [November 12, 2004, 7:29pm UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/24 "2004-11-12T19:29:50Z")
> [@Plynck](#): > > Then please explain to a layperson: > How can planes fly upside down? (cont’d) The same way they can fly right side up. Velocity at Angle of Attack of the wing creates the Force of Lift. The Force of Lift is equal to and dependent on the Velocity at Angle of Departure (of the air mass from the trailing edge of the wing. The best shape of the wing is the most streamlined shape for any given airspeed and angle of attack. Flying that same wing upside simply makes it less streamlined. Raise the angle of attack and increase the power to make up for the increased drag and the upside down wing provides lift. [Picture](http://www.theautochannel.com/callahan/2001texas/harvick_car01.jpg) a NASCAR race car. The whole top surface of the car acts as a wing. The speed of the air parallel to the surface of the car provides lift through velocity alone (Bernoulli). Notice the air dams that prevent air from flowing under the car. Unlike an airplane wing, there is no opposing Bernoulli Effect on the car’s underside to counter this Bernoulli Lift. At a certain velocity, a perfectly streamlined care will lift due to Bernoulli’s force alone. Notice the little spoiler on the tail of the car. Compare the surface area of the spoiler to the whole surface area of the car. The spoiler deflects the airflow upwards. Newton. That tiny bit of Newton not only counteracts the Lift of Bernoulli, it creates enough extra Down Force to press the car onto the track. The upside of any wing is simply the side deflects the air mass most efficiently. Any wing that can deflect air in one direction can deflect the air in the opposite. Any wing can fly upside down. rwjefferson Peace through Liberty ---
**Author:** ![rwjefferson](https://avatars.discourse-cdn.com/v4/letter/r/a6a055/32.png) [@rwjefferson](https://boards.straightdope.com/u/rwjefferson)\ **Post date:** [November 12, 2004, 8:10pm UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/25 "2004-11-12T20:10:23Z")
> [@RM Mentock](#): > > Pressure involves matter changing direction Pressure is a Force. Matter changing direction is a Reaction to said Force. > [@RM Mentock](#): > > A Vector of Newton? A [Vector](http://dictionary.reference.com/search?q=Vector) is the Angle and Carrier of Force. Bernoulli’s formula only applies to Fluids traveling parallel to a surface. All other Force Angles (Vectors) are outside Bernoulli’s formula. Bernoulli is the carrier of Newtonian Force in Parallel Vector. Newton describes the Reaction to Force in all Vectors, including Parallel Vectors. rwjefferson Peace through Liberty ---
**Author:** ![rwjefferson](https://avatars.discourse-cdn.com/v4/letter/r/a6a055/32.png) [@rwjefferson](https://boards.straightdope.com/u/rwjefferson)\ **Post date:** [November 12, 2004, 9:37pm UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/26 "2004-11-12T21:37:45Z")
> [@Johnny L.A.](#): > > (quoting “a well known aerodynamicist”) > “There can be a lifting force without downwash; for instance, a bump in the floor of a wind tunnel experiences a lifting force.” There is indeed downwash behind a bump in the floor; the downwash dissipates sideways across the floor. A bump in an air stream leaves a wake. A better example of Bernoulli (lift without downwash) is the wind tunnel floor itself. As the airspeed over the floor increases, the air pressure on the floor lessens according to Bernoulli’s formula. Increasing airspeed over a surface increases lift. Bernoulli. The key to lift is not what happens to the departing air mass; the key is that the departing air mass gained its downward Force Vector by imparting equivalent Lift to the Wing. A wing in that same wind tunnel also creates lift. However, the lift generated by a wing is magnitudes greater than the lift generated by the floor. The critical difference is that the attack (Force) of the wing Accelerates air Mass Downward. The wing experiences Lift. Newton. Again, compare the surface area of a spoiler on a NASCAR racecar to the whole upper surface area of the car. That is the power of Newton over Bernoulli. rwjefferson – “an unknown amateurdynamicist” Peace through Liberty ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [November 13, 2004, 1:52am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/27 "2004-11-13T01:52:11Z")
> [@Q.E.D.](#): > > It isn’t that much of a stretch, and is, in fact, the current most-favored explanation in the world of higher physics. I suggest you read Brian Greene’s _The Elegant Universe_ for a more detailed, plain-language treatise of this and other aspects of QM and Superstring theory. It really is an excellent read. > > I don’t know this Carver mead you speak of, but a Google search on the name tells me only that he is a pioneer in semiconductor design. Perhaps you’d care to share this theory to which you refer? I’ve read Brian Greens’ book you mentioned and it is indeed an excellent read. Perhaps akin to Paul Davies’ material. which I recommend. Jake ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 14, 2004, 10:12pm UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/28 "2004-11-14T22:12:11Z")
> [@](#): > > A better example of Bernoulli (lift without downwash) is the wind tunnel floor itself. As the airspeed over the floor increases, the air pressure on the floor lessens according to Bernoulli’s formula. Increasing airspeed over a surface increases lift. Bernoulli. If we have an upwards force acting on the floor of the wind tunnel, then the floor of the wind tunnel is exerting a downwards force on something. If it were the air causing the upward force, then this would be a downwards force on the air, which would cause a downwash. If this is not the case, then what is exerting the force, and why doesn’t it react to the force the tunnel floor is putting on it? ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [November 14, 2004, 10:25pm UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/29 "2004-11-14T22:25:12Z")
> [@Chronos](#): > > If we have an upwards force acting on the floor of the wind tunnel, then the floor of the wind tunnel is exerting a downwards force on something. If it were the air causing the upward force, then this would be a downwards force on the air, which would cause a downwash. If this is not the case, then what is exerting the force, and why doesn’t it react to the force the tunnel floor is putting on it? That would appear to be the air beneath the floor, right? Although I wouldn’t exactly call that a downwash. ---
**Author:** ![rwjefferson](https://avatars.discourse-cdn.com/v4/letter/r/a6a055/32.png) [@rwjefferson](https://boards.straightdope.com/u/rwjefferson)\ **Post date:** [November 19, 2004, 1:41am UTC](https://boards.straightdope.com/t/bernoullis-principle/273459/30 "2004-11-19T01:41:08Z")
> [@Chronos](#): > > If we have an upwards force acting on the floor of the wind tunnel, then the floor of the wind tunnel is exerting a downwards force on something. If it were the air causing the upward force, then this would be a downwards force on the air, which would cause a downwash. If this is not the case, then what is exerting the force, and why doesn’t it react to the force the tunnel floor is putting on it? The Force acting on the floor of the wind tunnel is not acting upwards. The Force acting on the floor is Air Pressure downward. As the speed of the Air Stream increases, the Air Pressure decreases due to Bernoulli-Newton. It is not Pressing down with as much Force as it was when it was motionless. If there is stationary air above the Air Stream, it will be pulled into the air stream by the Pressure Difference. Areas of differing pressures tend to Equalize. If the air stream passes beyond a raised floor, there is no longer Velocity across a Surface. The Bernoulli factor of Newton ceases. The Pressure and Density rises. The additional Density is less buoyant than the surrounding air. The Air falls. This results in Downwash. As long as extra air Pressure does not seep under and lift the floor, there is no lift or lift induced downwash. I hope this helps. rwj [Previous page](https://boards.straightdope.com/t/bernoullis-principle/273459.md?page=1)