Va and weight?

[bucksmith]

I went round and round trying to come up with a way to explain this to the new student...with the help of my peers, I came up with this...Va is the speed at which you'll stall before you'll break...as you get lighter, you are operating further away from the critical angle of attack (you need less lift) therefore ya gotta slow it down to get the angle of attack back up and close enough to the critical angle of attack to allow you to stall before ya break...
basically its the dumbed down version of Rod Machado's explanation, you start with this to get 'em in the park then get a little more technical...

 

[shdw]

I don't see the corollary, myself, with the present subject.

I think because you are over analyzing it. Move more degrees = more g-forces. Drop weight from higher height = larger impact force. Physics aside the experiment will work, and I think, create a link in the students mind. Can anyone with lack of physics knowledge speak up on this?

I don't think all students understand that more degrees of movement = more g forces. As we both know, linking known to unknown improves the chances of them remembering. Everyone knows if you fall from a higher hight it impacts harder, even if they don't know a thing about physics. This is just a way to remember "more degrees = more g's."

Hah that rhymes, maybe that rhyme will work for others...more degrees = more g's!!! (Sorry, random drunk epiphany.)

 

[tgrayson]

linking known to unknown improves the chances of them remembering.

Yes, but more important than remembering is understanding. When the link you provide is a false one, you've given them the illusion of understanding without the reality of it. That isn't what teachers should do.

 

[shdw]

Yes, but more important than remembering is understanding. When the link you provide is a false one, you've given them the illusion of understanding without the reality of it. That isn't what teachers should do.

We do that all the time though. It is an easily fixed illusion should they pursue physics classes. Here is my thoughts on the outcome of such a statement through a variety of students (though not physically true, as we both agree):

1) The student that has taken and forgotten physics to never remember it again/will never take physics. Probably 50 percent of the population falls in here if not more. This may help them link the idea with no negative effect since a true physical understanding will never matter to them. This type of student will likely be easy to recognize by the instructor, they avoid math/logic.

2) Student that has/will take physics and understand it. Probably 25 percent of the population. For them, we can give the pure physical definition or just let them read pdxcfi's reply quoting aerodynamics for the naval aviator. This type of student should be easy to recognize by the instructor, they love math/logic.

3) Student that has/will take physics and doesn't get it. This explanation may help them/hurt them. A student that will require analysis on the instructors part to determine how to explain it. In some cases it will help, probably half of them, because it will trigger questions about angular acceleration/force which we can maybe help them straighten out. In the other half it may hurt by simply completely confusing them. A difficult type because they will border liking/hating or understanding/not understanding math/logic.

Conclusion: Of the 25 percent, difficult to determine, 12.5 percent will be hindered by this and 12.5 percent may be helped by it. About 25 percent will not, but the instructor should easily determine this 25 percent. About 50 percent will find it helpful.

What are your thoughts? I know my thinking is crazy, bare with it please.


Edit: One more thing: The relationship here is between angular acceleration and impact force. To my knowledge both vary with time and time varies with distance travelled. So is that correlation, even in a physical sense, really a bad/incorrect one?

 

[tgrayson]

We do that all the time though.

I don't and I'm sure a great many others don't either. It's our job to find a way to communicate without compromising the truth. If we can't, it's our failing, not the students. If you need to teach basic physics, then teach basic physics. If you need to teach algebra, then teach algebra. All the more value the student derives from having interacted with you.

If I can convey to the student new insight into Newton's laws of motion by relating them to something he actually cares about, I consider that as having given him a great gift. That's really more important than any aerodynamic insight I can provide, so I won't sacrifice the former to give him the latter.

 

[shdw]

I don't and I'm sure a great many others don't either. It's our job to find a way to communicate without compromising the truth.

I guess this is where I have a more radical or uncommon belief. I don't believe we need to worry as much about the truth as we need to worry about avoiding interference. After all, it is interference we are trying to avoid with the goal, "communicate without compromising the truth," right?

It is my belief that certain descriptions, while devoid from absolute truth, will get a point across to certain people without creating interference in their learning down the road. In this case, someone who doesn't learn through logical means will likely never analyze this sentence for its absolute truth. Thus, it will never interfere with their ability to be taught that absolute truth at a later date.

It is a theory in progress and I still don't know how to test it. So I am not claiming this to be right or wrong, I don't know. Thanks for the thoughts on it though, I always enjoy input; good or bad.

 

[tgrayson]

After all, it is interference we are trying to avoid with the goal, "communicate without compromising the truth," right?

To some degree, yes. Falsehood does lead to interference, i.e., contradiction, which is how falsehood is detected. But you can have interference and still have truth. e.g., steering a car interferes with the proper usage of the yoke in the airplane. Both are "true", yet interfere with each other.