tgrayson
New Member
- The aerodynamic force is merely the resultant of the lift and drag vectors.
- The aerodynamic force can be decomposed into lift and drag vectors
Why do you think that either one of these statements is more true than the other?
Bernoulli and Low Pressure
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Why do you think that either one of these statements is more true than the other?
splash
your social justice comic center
Is air or anything in this gap?
News to me.
This is due for another thread and I have a problem using the word "weight" instead of "gravity" because weight is a measurement of the force called gravity therefore weight is not a force.
splash
your social justice comic center
If the air is not there and a suction device is needed to KEEP AIR ATTACHED then this gap is a vacuum and the device is keeping the vacuum from forming. A vacuum is not a force. Agreed?
tgrayson
New Member
It's an area of reverse flow, so yes, there is air there.
Hmmmm, I wonder why weight is measured in Newtons, which is a unit of force? I wonder why when I step on piece of rotten flooring, my foot falls through, yet a kitten can run right over it?
Air IS there.
No, the suction is there to prevent an area of high pressure.
splash
your social justice comic center
Hmmmmm, I wonder why my weight is different on the moon than the weight on earth. Newton is a unit of force just like your weight is a unit of force. It's Like saying, do you want to measure that stick in feet or yards.
This is why it is safe to say that a brick weighting 9.8 newtons=1 kilogram on earth but on a massive planet the brick would weight more!
Which is correct?
A) The gravitational force is keeping things on earth.
B) Weight and newton force is keeping things on earth.
I donno :dunno: how to explain it anymore. We'll have to agree to disagree on the "gap" thingy.
tgrayson
New Member
Because the magnitude of the force is the interaction between the acceleration produced by the gravitational field and the mass of the object.
You can disagree if you want, but you wouldn't be able to mathematically work even elementary mechanics problems without understanding that you must multiply the mass of an object by the acceleration due to gravity before you can calculate the result of multiple force vectors.
Well those interpretations are both fine, but realize though that you didn't claim lift or drag as a force because they in fact are not forces and thus only three forces.
Minuteman
I HAVE STRONG OPINIONS ABOUT AUTOMOTIVE LIGHTING!
Well those interpretations are both fine, but realize though that you didn't claim lift or drag as a force because they in fact are not forces and thus only three forces.
How does an airplane propel itself forward in an airmass?
How does an airplane support its weight while in flight?
If you're going down that path, there is only weight and momentum exchange with the atmosphere. Two forces.
It propels itself forward with a thrust force, it is pulled to the earth with a force of weight, and the aerodynamic force from it moving through the air is the what gives it both lift and drag. I don't see how you make things 2 forces?
Unless you speak of a glider then I am unsure.
Splash/tgray: This area of separation, would it not be at a lower pressure caused by the fast flow of air above? Doesn't this area of lower pressure act to suck down on the air above resulting in the spiraling of air? Wouldn't it be compared to air flowing quickly off a cliff in that the air shoots off the cliff and exhibits a suction on the air on the face of the cliff, sucking it up into the airflow above creating a low pressure just off the face of the cliff and once again spiraling the air just like that off the wing nearing stall? Wouldn't this suction then have the same principles of an imperfect vacuum?
Maybe I am just completely out of whack here I am not sure but it seems your both arguing this and both to some extent right. The area where separation occurs isn't empty space, splash, but instead an area of lower pressure which is exhibits properties of an imperfect vacuum, tgray. It just isn't a perfect vacuum devoid of all air, but it is still an area of low pressure which is causing the airs circulation as it spirals off the wing.
As for weight not being a force...
I was referring to the three forces being weight, thrust, and aerodynamic force which acts off the CP or for calculation simplicity off the AC.
splash
your social justice comic center
These are your words Grayson, meaning nothing there and a simple vacuum which is nothing is taking up this space.
I think you are ramming to many thoughts up on this such as Newtons 2nd law of motion. Keep it simple. At my best efforts I'm trying to explain that weight and newtons are units of measurements of an actual force being applied. Best efforts have just arrived:
My first 7 inches, ...does that sound like a force or unit of measurement?
Do you see the light at the end of the tunnel or do you need another 7 inches. It don't matter how hard you ram it to see the light at the end of the tunnel because you will not get a different unit of measurement out of how hard you thrust it, lift it, or drag it! 
Gravity is the force pulling an aircraft down. The other 3 are also forces. To say that weight is the force pulling an aircraft down is incorrect because it is a simple unit of measurement of the force we call gravity.
splash
your social justice comic center
I believe the text books are keeping the focus on the plane rather than the earth in this "force called weight" which seemed odd in the beginning of my training. I didn't question it and just went with the flow to pass at the time. I realize an error I made saying weight is a unit of measurement which it is not. However, I believe the word weight can be used loosely describing all units of measurement in different directions. Yep, I know I'm up against some text books here. Can we say that weight (as a force) is what is holding us to the earth? Is weight really what is pulling down on an aircraft? My answer would be no, gravity is holding us to the earth, pulling down on an aircraft and it can be weighed in pounds. Lift is what is holding the aircraft up and it can be weighted in newtons. Thrust is pulling it forward and can be weighed in horse power. Drag is pulling it back and it can be weighed in grams. On the other hand, it is confusing to say that weight is pulling an aircraft down and it can be weighed in pounds.
tgrayson
New Member
Well those interpretations are both fine, but realize though that you didn't claim lift or drag as a force because they in fact are not forces and thus only three forces.
Well, they are forces and every bit as real as the aerodynamic force. Any force can be decomposed into two separate forces along any two perpendicular axes you choose and those components are just as real as the resultant.
There ARE four forces affecting an airplane because they are defined so. You're really going to mess yourself up if you choose not to understand this.
tgrayson
New Member
A word salad.
Either you have a hopelessly confused notion of basic physics or you're just yanking my chain by throwing out random words in strung together in sentences. I suspect the latter, so I'll withdraw from the conversation.
tgrayson
New Member
The area behind the point of separation has a higher pressure than points in front of it...it's this higher pressure that causes the direction of airflow to reverse, which is what defines separation. It isn't anything remotely resembling a vacuum.
moxiepilot
Well-Known Member
Before I get back to this question, I wanted to point out how far the conversation has strayed, not that that is a bad thing. But, I do agree with Tgray on a lot and shudder at some of the arguments which have been made including the statments about vaccuums and gravity not being a force involved in flight.
I don't even want to start to argue some of those basic physic principlies at this time. It makes my head hurt.
conceptually I agree - go from a known to unknown, ensuring the correct terminology/definition is explained and understood.
If we are to use a vaccuum cleaner in this example, it really must be understood that what we are actually discussing is a pressure differential cleaner to remove dirt from our rugs.
Note how carefully the above words were chosen. I did not say that we are using a pressure differential cleaner to "suck" dirt from our rugs. There really is no "suck" it is a difference of pressure between the exterior canister and the interior canister which creates movement of air molecules from the higher pressure system to the lower pressure system. The dirt just happens have little mass and is "going with the flow (of movement of air.)"
So to get back to how there can be a negative transfer of learning (and by that I think you mean "how teaching this principle can negatively affect the learner") - using the vaccuum cleaner as an example of what is known could impact the learner if it is never explained as to what it actually is (pressure differential cleaner)
I think we may split hairs over the subject, as I may have assumed that you would not be explaining the difference between a vaccuum and a vaccuum cleaner to the student. But I also think you may see my point:
If a student has an incorrect understanding of the "known object" used to teach from the known to the unknown, then while they may grasp the concept they might not ever grasp the reality. I might look at the last 20 posts or so for a good example...
I have a BIG problem with that statement. There are 4 forces of flight. From my quick scan of the ensuing argument the force of Gravity seemed the one most debated. I don't even know where to begin and cannot stop shaking my head that such a preposterous statement could be made.
So let me ask this, Why does air pressure at the surface weigh 14.7 pounds per square inch/29.92 mb? The force of gravity is acting upon the column of air towards the center of the Earth. If you throw a baseball, does it not drop to the ground eventually?
It was argued that Gravity is a "weight", to that I ask what "weight" acted upon the baseball as it fell to the Earth? None, it was a FORCE.
After writing all that I realize splash is arguing that Lift and Drag are acting through the CP, combining the two forces into one which he terms Aerodynamic force. That force however can be broken into the two separate components, Lift and Drag - kinda like breaking down Water into its simplest elemental components - Hydrogen and Oxygen. You can call it whatever you want to, but it doesent mean that the two most elemental vectors do not exist...
All I have to say (on my soapbox) is never sacrifice truth. As teachers we must find the manner to make it simple enough to understand. What that means perhaps, is to break down the steps further - to their elemental properties - which might take longer; but, at no point does it ever lead to misunderstanding because of a step omitted to make it "less complex"
I don't even want to start to argue some of those basic physic principlies at this time. It makes my head hurt.
conceptually I agree - go from a known to unknown, ensuring the correct terminology/definition is explained and understood.
If we are to use a vaccuum cleaner in this example, it really must be understood that what we are actually discussing is a pressure differential cleaner to remove dirt from our rugs.
Note how carefully the above words were chosen. I did not say that we are using a pressure differential cleaner to "suck" dirt from our rugs. There really is no "suck" it is a difference of pressure between the exterior canister and the interior canister which creates movement of air molecules from the higher pressure system to the lower pressure system. The dirt just happens have little mass and is "going with the flow (of movement of air.)"
So to get back to how there can be a negative transfer of learning (and by that I think you mean "how teaching this principle can negatively affect the learner") - using the vaccuum cleaner as an example of what is known could impact the learner if it is never explained as to what it actually is (pressure differential cleaner)
I think we may split hairs over the subject, as I may have assumed that you would not be explaining the difference between a vaccuum and a vaccuum cleaner to the student. But I also think you may see my point:
If a student has an incorrect understanding of the "known object" used to teach from the known to the unknown, then while they may grasp the concept they might not ever grasp the reality. I might look at the last 20 posts or so for a good example...
I have a BIG problem with that statement. There are 4 forces of flight. From my quick scan of the ensuing argument the force of Gravity seemed the one most debated. I don't even know where to begin and cannot stop shaking my head that such a preposterous statement could be made.
So let me ask this, Why does air pressure at the surface weigh 14.7 pounds per square inch/29.92 mb? The force of gravity is acting upon the column of air towards the center of the Earth. If you throw a baseball, does it not drop to the ground eventually?
It was argued that Gravity is a "weight", to that I ask what "weight" acted upon the baseball as it fell to the Earth? None, it was a FORCE.
After writing all that I realize splash is arguing that Lift and Drag are acting through the CP, combining the two forces into one which he terms Aerodynamic force. That force however can be broken into the two separate components, Lift and Drag - kinda like breaking down Water into its simplest elemental components - Hydrogen and Oxygen. You can call it whatever you want to, but it doesent mean that the two most elemental vectors do not exist...
All I have to say (on my soapbox) is never sacrifice truth. As teachers we must find the manner to make it simple enough to understand. What that means perhaps, is to break down the steps further - to their elemental properties - which might take longer; but, at no point does it ever lead to misunderstanding because of a step omitted to make it "less complex"
tgrayson
New Member
This isn't directed at you, but one measure of recognizing severely flawed understandings of the nature of physical phenomena is when someone mixes together incompatible units of measurement. Splash up above was quantifying units of force variously in Newtons, Grams, and Horsepower, not recognizing that these are respectively units of force, mass, and power.
You cannot throw gravity into force calculations alone, because the only measure we have of gravity is the acceleration due to gravity, 9.8 m/s^2. That isn't a force, it's an acceleration. It doesn't become a force until you multiply that acceleration by a mass. Once you do that, you have its weight, and you then have a unit of measure that can be included in force calculations.
Pick up any elementary physics book and you won't see gravity included as a force except when multiplied by the appropriate mass, often expressed as "mg".
drunkenbeagle
Gang Member
More correct to say a 1 kg brick exerts a force of 9.8 kg meters per second squared on earth. g = -9.8 m/s^2. F=ma and all that.
weight is most definitely a force.
In the English system, the pound is both the unit of force and mass on earth.
Tgray: It is? Would a high pressure area push air away from it and not pull air into it?
I am not saying your wrong because I am not sure. I am asking to try and understand how an area of high pressure could cause such an air flow, it doesn't make sense to me.
Moxie: I agree with the gravity deal, I was discussing aerodynamic force not weight/gravity argument.
Negative transfer of learning means when something is taught that interferes with information that will be given later on and causes that later information to be more difficult to grasp. In this case referring to it as a big sucky thing versus a pressure differential device doesn't give any faulty comprehension because one already views a vacuum as a big sucky thing.
It can however help the student be more receptive to something they might view as complex and confusing, you are simply trying to remove confusion with this known information. Explained right the student would come away with this, the wing is sucked up into the air because of a pressure difference and it is this pressure difference that causes lift.
Your one way of explaining lift may work for most of your students but I think it is extremely important that we have various methods. For some students the words "pressure differential" alone would make their head spin and no matter what you say if you come back to this point they will always feel as though something is missing. For a student like that a relation to a vacuum, ignoring how the vacuum actually works to avoid confusion once more, might help.
I still don't see any negative transfer that would occur from this and I suggest you research that idea a little more as it is one of the biggest hindrances to continued learning. Understanding how it works and what will and won't bring about a negative transfer can drastically improve your ability to organize lesson ideas for your students. An example: teaching pitch for altitude or allowing a student to use pitch for altitude early on can have a negative transfer when the student falls behind the power curve for slow flight or gets slow on final approach. (Sorry mike I had to!)
I am not saying your wrong because I am not sure. I am asking to try and understand how an area of high pressure could cause such an air flow, it doesn't make sense to me.
Moxie: I agree with the gravity deal, I was discussing aerodynamic force not weight/gravity argument.
Negative transfer of learning means when something is taught that interferes with information that will be given later on and causes that later information to be more difficult to grasp. In this case referring to it as a big sucky thing versus a pressure differential device doesn't give any faulty comprehension because one already views a vacuum as a big sucky thing.
It can however help the student be more receptive to something they might view as complex and confusing, you are simply trying to remove confusion with this known information. Explained right the student would come away with this, the wing is sucked up into the air because of a pressure difference and it is this pressure difference that causes lift.
Your one way of explaining lift may work for most of your students but I think it is extremely important that we have various methods. For some students the words "pressure differential" alone would make their head spin and no matter what you say if you come back to this point they will always feel as though something is missing. For a student like that a relation to a vacuum, ignoring how the vacuum actually works to avoid confusion once more, might help.
I still don't see any negative transfer that would occur from this and I suggest you research that idea a little more as it is one of the biggest hindrances to continued learning. Understanding how it works and what will and won't bring about a negative transfer can drastically improve your ability to organize lesson ideas for your students. An example: teaching pitch for altitude or allowing a student to use pitch for altitude early on can have a negative transfer when the student falls behind the power curve for slow flight or gets slow on final approach. (Sorry mike I had to!)
tgrayson
New Member
Sure, just like the atmosphere where high pressure air flows out of the "H" into the "L", causing wind. At least that is the tendency. If the low pressure air has momentum, it can make some headway against a high pressure area, but it will be continually decelerating. This is similar to throwing a ball up, even though its weight wants it to fall. The ball will fly upwards, decelerating, until it comes to a stop then reverses direction.
splash
your social justice comic center
Great picture shdw. Can anyone tell me what the big black hole is just above the trailing edge? It looks very empty to me. The eye of the storm or something that cleans the wing?