AirPlane on a Teardmill and Mythbusters

[Superjag]

Ok, I have been able to resist the urge to get involved in this since the first time it was posted on the old forum, but to quote that nautical poet Popeye the Sailor, "I can't stands no more!" THE PLANE WILL FLY. It is simple physics. The speed of the wheel has absolutely no bearing on the planes ability to create thrust. Want to prove it to yourself? Try this:

1. Go to a large aiprport or any other location with one of those moving walkways. (This will be your "treadmill".)

2. Put on roller skates and stand on the moving walkway facing the opposite direction that it is traveling. (You are the "plane". The skates are your "landing gear".)

3. Now stick out your arms to each side like a plane's wings. Have a friend stand on either side of you but not on the treadmill and hold on to your outsretched arm. (Your friends are now the plane's "jet engines".)

4. Now have your friends walk forward. This is the thrust of the engines. Because the thrust generated by your "engines" is pushing on the wings (and not the wheels!!!!) you will move forward. If your friends move faster, so will you. The walkway can spin faster and faster , but it will not matter at all. Only the wheels are spinning at the same rate as the walkway/treadmill. You (the plane) will continue to move forward at whatever rate your friends are pulling you along, no what matter the speed of the walkway and your wheels. If your friends can run 100 mph, you will go forward at 100mph. The only way this would not be true is if your wheel bearings have a bunch of resistance in them to the point that your friends could not overcome the drag caused by the friction of the bearings, but that is not what the scenario describes.

NOW does this make sense?!

 

[Mafesto]

I'm sorry, but I cannot come up with any simpler analagies that what has already been stated.

I lack the eloquence to continue this debate without becoming condocending.

I apologize that we have failed to provide an adequate explanation supporting our thesis.

As was pm'ed to me earlier.....
"It is time for me to agree to disagree"

See ya on the snow!

 

[Supplicate]

THE PLANE WILL FLY. It is simple physics.

It is simple physics, net movement has to be in the forward direction to take off.

1. Go to a large aiprport or any other location with one of those moving walkways. (This will be your "treadmill".)

Your scenario is flawed because the walkway is at a static speed and it can't match your speed as the "Thust" is applied.

 

[Supplicate]

I'm sorry, but I cannot come up with any simpler analagies that what has already been stated.

I'm not asking you to come up with simpler analogies (IMO some of you are over simplifying this one ), just asking you to explain why you are thinking about it the way you are.

Lets look at things that have been said:

1) The wheels aren't under power.

Okay, so they don't have a drive shaft driving them. But, there is force being applied to them. Therefore in the simplest definition they are under power. Lets use the skateboard as an example of this. The rider has to propel the board by pushing against the ground (their thrust) but, if you think about it by force transfer it goes through their body into the board, from the board to the trucks, down to the axles. If you look at it in a micro perspective instead of a macro perspective, there is force (power) being applied right there.

2) Wind speed is occuring over the fuselage.

Okay, this only happens (yet again I'll say this) if the net movement is in the forward direction.

Have any of you seen the artist that used an airplane to do paintings? They tied the fueselage down to the ground, locked the wheels, and cranked up the thrust. The artist then threw paint into the jet wash and let it spray however it would onto the canvas. Did that airplane take off when thrust was being applied? No! Simply because net movement was zero.

3) The belt moving under the tires have no effective resistance to the planes forward movement.

Sure, if you look at forward movement in relation to the conveyor. The wheels and the fuselage are moving forward in relation to the surface of the conveyor which moves independently of the surface of the earth.

Now, if you look at forward motion in relation to the surface of the earth (assuming the conveyor is perfectly matching all forward motion of the plane) the net movement is zero.

Look at it like a car on a dyno, why do you think they have to put huge fans in front of the radiators so the car's don't overheat? Thats right, there is no air movement over the body of the car! This one also directly relates to number 2.



I'll let you guys stew over this one. And remember, this is all in fun as I have nothing better to do right now

 

[Superjag]

It is simple physics, net movement has to be in the forward direction to take off.


Your scenario is flawed because the walkway is at a static speed and it can't match your speed as the "Thust" is applied.

Speed or acceleration of the treadmill is completely irrelevant. Think about the walkway going faster and faster. The wheels will spin faster and faster, but you will continue to travel forward (ah, get it, net forward movement?) at whatever speed your friends walk forward. They are your thrust. If the treadmill is going 1,000,000 miles an hour backward, but your friends are pulling you forward at 100 mph, guess how fast you are going. 100 mph. People standing around at the airport will see a guy being pulled at 100 mph, no matter what speed the treadmill is traveling at because (again) only the wheels are affected by the treadmill. Your speed is determined by your friends and their thrust.

I will repeat: It is VERY simple physics.

 

[TooHotPoo]

your brain is flawed... how can you not understand this??? its so simple... are you fukin with everyone or are you serious in your argument that the plane wont take off?? air speed is what makes the damn plane fly.. air speed is what the engines have to overcome not the damn conveyor speed, if there was a tail wind too great for the engine to overcome to get the plane to get lift then hell no the plane isnt going to fly.. that is the ONLY way it wont !!

 

[Supplicate]

but you will continue to travel forward (ah, get it, net forward movement?) at whatever speed your friends walk forward. They are your thrust.

So you are measuring the speed independent of the treadmill because your "thrust" is actually tied to the surface of the earth. In this case the plane would take off because your net movement is forward (and I have stated that would happen several times before).

Now, if your thrust wasn't tied to the surface as in your experiement but rather independent of the surface (as with an airplane) and as in this experiment the speed of the conveyor will always match the forward speed (as measured at the wheels) you get zero net movement and therefore will not take offf.

 

[Superjag]

And you're wrong in your response to Mafesto. The wheels are in no way under power. The thrust is acting on the wings, which in turn push the fuselage, and everything attached to it. The wheels are just a mechanism to overcome friction with the ground. The would not have to turn at all if they were made out of ice or some super slippery compound that could just slide along the ground. The turning of the wheels only occurs BECAUSE the plane is moving forward. They in no way CAUSE the plane to move forward. That is why what is happening between the wheels and the treadmill is completely irrelevant to the forward movement of the plane.

 

[Supplicate]

your brain is flawed...

Okay smart@ss, how is my brain flawed for looking at this from all angles?

in your argument that the plane wont take off?? air speed is what makes the damn plane fly..

have you not read my responses and how many times I have said exactly that. but you have to have net movement in the forward direction to get airspeed, jet engines do not move the air over the wings

air speed is what the engines have to overcome not the damn conveyor speed

what about rolling resistence? What about friction? What about reverse speed of the conveyor (essentially an infinite tail wind)?

if there was a tail wind too great for the engine to overcome to get the plane to get lift then hell no the plane isnt going to fly.. that is the ONLY way it wont !!

exactly read the last section of my response, the conveyor is acting as an infiintie tail wind

 

[Supplicate]

The wheels are in no way under power.

Again, you are looking at it in the Macro, not the Micro.

If you look at a car, a skateboard, a plane, a snowmobile, it doesn't matter what, right where the tires or track contact the surface there is no difference between being driven by a drive shaft or being driven because of thrust.

 

[Superjag]

So you are measuring the speed independent of the treadmill because your "thrust" is actually tied to the surface of the earth. In this case the plane would take off because your net movement is forward (and I have stated that would happen several times before).

Now, if your thrust wasn't tied to the surface as in your experiement but rather independent of the surface (as with an airplane) and as in this experiment the speed of the conveyor will always match the forward speed (as measured at the wheels) you get zero net movement and therefore will not take offf.

Wrong again, shooter. The thrust is created by and acting upon air molecules which are in no way connected to the treadmill or its direction of travel. That is why using the friends is analagous to the thrust of the engines. The thrust has nothing to do with the wheels or the ground, and that is why the speed of the treadmill and or the wheels has no bearing on the equation.

 

[Scott]

WILL the conveyor belt be at a constant speed throughout the takeoff attempt?

Will it be at a slow speed, or a fast speed.


This has nothing to do with the airplane but.....Given that the escalator is moving in slow speed and not HIGH speed...With the rollerskate analogy...Will it be initially easier for the buddies to begin rolling you forward from the initial start while on the escalator is in motion

Or will it be easier to get you rolling from a dead stop if the escalator was turned off and it wasn't moving?

In both scenarios the buddies are holding the skater's arms and are ready to pull. The only variable that is different is a slow moving sidewalk vs a statioinary sidewalk. A 3rd test could be to have the sidewalk moving faster at saaaayyyy.... double time.

Which one takes more initial force to get the person on the rollerskates to move past some arbitrary fixed object next to it (and not on the conveyor belt/sidewalk)? Me thinks it might be easier to pull him forward when the belt is already moving.

 

[Meatman]

first off the wheels are under power...not being powered second off thrust of an airplane is tied to the atmosphere and i dont care how fast the wheels are spinning the plane is going to move forward....

supplicate can't be serious

 

[Superjag]

supplicate can't be serious

I hope you are right.

 

[Supplicate]

That is why using the friends is analagous to the thrust of the engines.

Hmmm... so your friends that are solidly rooted to the earths surface pushing on your body, thereby solidly tying your body to the earths surface act in the same way as a jet engine pushing on air that is completely 100% independent of the earths surface?

WILL the conveyor belt be at a constant speed throughout the takeoff attempt?

In the original question posted how ever long ago it was, it stated (IIRC) that the conveyor belt will always match the speed of the wheels, which means it is not at a static speed.



Guys, welcome to the age old question of relative motion. Years ago one of my physics proffesors said if you could invent a machine to measure relative motion (do you move through the room or does the room move around you?) you would become a billionaire overnight.

Guessing from some of your responses, this machine should have been invented and built centuries ago because it is "simple physics."

 

[TooHotPoo]

first off the wheels are under power...not being powered second off thrust of an airplane is tied to the atmosphere and i dont care how fast the wheels are spinning the plane is going to move forward....

supplicate can't be serious

I think he is fukin with everyone, its really not that hard to understand.... is it?

 

[Supplicate]

the plane is going to move forward....

move forward in relation to...

the conveyor? won't take off
the earth's surface? will take off
you? depends on which direction you are headed and at what speed
a bird flying the oposite direction? might take off.

...

 

[EastcapeAngler]

I think he is fukin with everyone, its really not that hard to understand.... is it?

..I dunno.... I was one stubborn ARSE about the subject til I changed MY mind!

 

[Superjag]

Guys, welcome to the age old question of relative motion. Years ago one of my physics proffesors said if you could invent a machine to measure relative motion (do you move through the room or does the room move around you?) you would become a billionaire overnight.

Guessing from some of your responses, this machine should have been invented and built centuries ago because it is "simple physics."

Dude, this is not a "relative motion" issue, at least not in the sense that you are implying. The plane, its wings, and it's wheels are all moving forward at the same speed relative to the air around it. What is happening on the ground has no affect on the speed in relation to the stationary air air molecules, which are not on the treadmill and not moving backward.

 

[EastcapeAngler]

..DO I HAVE to PM the moderator??..