Best Tech. Debate: Groundspeed vs. airspeed

[JAZN 5,000+ posts]

THANK YOU! I'm glad someone noticed that... lol

lol I didn't even notice that till after I figured out the answer, silly of me.

 

[squeak9798 5,000+ posts]

Or, think of it this way.......

Place a matchbox car on a treadmill. Now try to push the car forward with your hand.

What happens to the wheels doesn't matter since you are applying force (thrust) to the vehicle itself and not the wheels directly. The wheels just spin.

 

[Nikuk 5,000+ posts]

http://forums.caraudio.com/vb/showthread.php?p=1322637#post1322637

 

[Chevyaudio 5,000+ posts]

Or, think of it this way.......
Place a matchbox car on a treadmill. Now try to push the car forward with your hand.

What happens to the wheels doesn't matter since you are applying force (thrust) to the vehicle itself and not the wheels directly. The wheels just spin.

that made the most sense, I stand corrected, The plane will take off. Thanks Squeak. I dont know what i was thinking.

 

[Acidburn 5,000+ posts]

Or, think of it this way.......
Place a matchbox car on a treadmill. Now try to push the car forward with your hand.

What happens to the wheels doesn't matter since you are applying force (thrust) to the vehicle itself and not the wheels directly. The wheels just spin.

thats a **** good way to put it squeak

 

[AllStar1500bd 5,000+ posts]

"As long as plane velocity is greater than air velocity, the plane will take off"

Makes sense. From what I understood in the first description, there was no propulsion on the plane.

And Black_Jesus, you need to take a chill. You act like you invented the myth or something.

 

[fb4076 10+ year member]

this probably has already been said, but I didn't feel like reading through the majority of this. The plane will still be moving forward. The conveyor belt would still have to be just as long as the normal runway, because the plane will move forward, causing the pressure differences necessary to take-off. The wheels will just be spinning on the conveyor belt at twice as fast as they would on a normal takeoff.

 

[lbridges 10+ year member]

While that's a good comforting feeling, common sense (which should always be noted) dictates that plane who's bearings were bad enough that it would have any notable effect on the foreward thrust of the engine would have never made it to the runway in the first place. Either due to someone saying "Hey! That planes wheels are ****ED UP!" or the simple fact that they would probably be so bad that the plane simply would not have be physically able to taxi out to the runway.
Hey if you don't agree, just ignore me I'm just an HVAC technician...

job has no relation to common sense or brain power, and actually I do agree. I just pointed out scenarios where everybody could be right given one could make up whatever assumptions were not provided in the problem.

In the AVweb site article the author says "My comment: Notice that the question does not state that the conveyor's movement keeps the airplane over the starting position relative to the ground, just that it moves in the direction opposite to any movement of the airplane."

I then note that the question also does not state the conveyor movement fails to keep the plane at any speed below that necessary to take-off. I just made up assumptions that differed to produce a no lift scenario - say for example the plane used skids - because it normally flew on/off ice fields....hey, I said I was a physicist and most people think (know?) physicists have no common sense (my wife included).

But a common sense thing did occur to me, who would build a feedback loop controlled belt for a runway.

 

[Rmsanger 10+ year member]

Bam how does my weiner taste now ladies! Trump card. I would think this debate is assuming too many things i.e. head wind speed and direction, weight of plane, slope/angle of wings, etc... 150 mph thrust may not perfectly offset the 150 mph ground velocity.

 

[theCybe 5,000+ posts]

1" from the center of a record spinning 33 rpm, pi*r^2 = the distance traveled in one revolution from a static POV.

10" inches from the center of a record spinning 33 rpm, pri*r^2 = the distance traveled on one revolution from a static POV.

Is the record spinning faster at the outside of the record?

If a plane travels 1 mile on the ground, it has moved one mile.

If a plan travels "1 mile" in the air at 30,000' and lands, has it traveled one mile on the ground?

 

[theCybe 5,000+ posts]

"As long as plane velocity is greater than air velocity, the plane will take off"
Makes sense. From what I understood in the first description, there was no propulsion on the plane.

And Black_Jesus, you need to take a chill. You act like you invented the myth or something.

velocity is not only a measure of 'speed.'

 

[theCybe 5,000+ posts]

it will take off, but not 'fly.'

 

[1990black300zx 10+ year member]

it will take off, but not 'fly.'

sure it will. the plane will move forward and accelrate until it reaches it's takeoff speed, end of story. If you haven't read the link i posted in the last page(others have posted it as well), READ IT. If you have read it, and still think it won't fly, RE-READ it. It clearly explains why it will fly.

the fact that the runway is moving backwards has no effect on whether the plane moves forward or not.

 

[Black_Jesus 10+ year member]

"As long as plane velocity is greater than air velocity, the plane will take off"
Makes sense. From what I understood in the first description, there was no propulsion on the plane.

And Black_Jesus, you need to take a chill. You act like you invented the myth or something.

hey, i just hate idiots //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
correction.. i hate idiots who refuse to learn if they are wrong //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

i cant help if im right the majority of the time. so take a chill, sit back, and be enlightened //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[UndercoverPunk 5,000+ posts]

job has no relation to common sense or brain power, and actually I do agree. I just pointed out scenarios where everybody could be right given one could make up whatever assumptions were not provided in the problem.
In the AVweb site article the author says "My comment: Notice that the question does not state that the conveyor's movement keeps the airplane over the starting position relative to the ground, just that it moves in the direction opposite to any movement of the airplane."

I then note that the question also does not state the conveyor movement fails to keep the plane at any speed below that necessary to take-off. I just made up assumptions that differed to produce a no lift scenario - say for example the plane used skids - because it normally flew on/off ice fields....hey, I said I was a physicist and most people think (know?) physicists have no common sense (my wife included).

But a common sense thing did occur to me, who would build a feedback loop controlled belt for a runway.

You really should post more.