Critical Thinking 101

[miketsp]

OK, so, if I were to put a really big can on a very, very accurate scale with its open end pointing to one side, and then put my hand inside the can it would weigh more?

the K-westioner

No, your hand has external support (wrist, arm, body, floor where you're standing). It is not being supported br the air inside the can.
In the case of the bird it derives it's lift from the air inside the object. This air is accelerated downwards and hits the floor thus.
If you want a similar analogy, try thinking about a (very) large cargo plane big enough to hold a chopper.
The chopper is initially at rest and you will surely agree that it's weight is aded to the weight of the plane.
The chopper starts up and goes into hover mode at a height of one foot above the floor of the plane.
The downwash from the blades is supporting the chopper and hitting the floor directly - action and reaction, right.
Now we assumed a big plane so the chopper gains height until there is no ground effect but the chopper is supported against the air mass and in turn the air mass is supported by the floor of the plane.
To an external observer outside the plane, nothing changed other than momentary peaks and dips as the chopper accelerated up and deaccelerated.

 

[Rick Murchison]

Y'all's interesting theoretical conjecturing is sorta fun to watch.
Here's a fact - make of it what you will...
Bees are sold by the pound, in boxes with screen sides. For accurate weighing you have to do it when the bees are all calm and not flying around inside, or you'll get a false (light) weight.
If you put the screen-sided box of bees in a closed container, however, and then weigh that container, the whole thing will weigh the same whether the bees are calm or agitated and flying around.
(This is consistent with what miketsp is saying)
Rick

 

[H2Andy]

Bees are sold by the pound, in boxes with screen sides. For accurate weighing you have to do it when the bees are all calm and not flying around inside, or you'll get a false (light) weight.

this is the sort of evidence that wins trials

love it

 

[do it easy]

Geez Andy! The Florida courts will accept threads on :sblogo: as admissible evidence?

 

[H2Andy]

alas, it would be hearsay



but i can subpoena Rick down to Florida (long process, but it can be done), and get him on the stand ... and then ...

he testifies in PERSON!

 

[Green_Manelishi]

The ability to sift facts and arrive at a correct solution is a basic skill in scuba diving. So, I thought this conversation which was overheard on my flight from the Mainland to Hawaii would provide some grist for the analytical grinder. For what it is worth the airplane was a nearly new B-767-300.


Diver? A (at about half way across the pond): Boy if it wasn't for burning so much fuel this airplane would be heavier when we land in Honolulu that when we left Los Angeles.
Diver? B: Why do you say that?
Diver? A: Have you seen all the people using the lavatories? They must have peed gallons, and gallons. That is all going into the holding tanks. You know they don't drain them overboard in flight any more.
Diver? B: No you ninnie; the airplane will be lighter. In addition to the fuel burned those people now have lighter bladders. And, have you seen the passsengers chowing down? The galley must be empty by now.
Diver? A: Of course, you are right, I should have known. The airplane will be lighter! You always were smarter than me.

So; what say you: Lighter? Heavier? Why?

Who is correct?

Unless something falls off of the aircraft, it won't be lighter or heavier. It will weigh the same as it did on takeoff. It's the cargo, fuel, etc. that will vary.

 

[The Kraken]

Ya see, Green got to the crux of the question.
It's about the weight of the airplane, not it's contents or anything else.
Unless one specifies the parameters.
How much does the airplane weigh?
Now, given the person asking the question may not be a pilot or flight engineer . . .
KISS . . .

the K-lobotomy

 

[Rick Murchison]

alas, it would be hearsay



but i can subpoena Rick down to Florida (long process, but it can be done), and get him on the stand ... and then ...

he testifies in PERSON!

No need to go to all that trouble... I accept cash
Rick

 

[AXL72]

The reason of whether the bird in a plane adds measurable weight or not lies in whether the scale is imersed in the fluid (air or water) being displaced or not. For the fish in a bowl of water, the scale is outside the fluid, so the weight increases. If the scale were immersed in the bowl of water, the fish would not add any measurable weight change.



Sorry to deviate off topic from mr. K's KISS.

 

[miketsp]

The reason of whether the bird in a plane adds measurable weight or not lies in whether the scale is imersed in the fluid (air or water) being displaced or not. For the fish in a bowl of water, the scale is outside the fluid, so the weight increases. If the scale were immersed in the bowl of water, the fish would not add any measurable weight change.



Sorry to deviate off topic from mr. K's KISS.

No, it depends whether or not the fluid (air or water) supported by the container is in turn supporting the bird/fish.
Immersion is not sufficient criteria as proven by the Kraken's post where he just stuck his hand in the can. (Post #57).
The hand is not supported by the air in the can but by an external structure.