That plane, and it taking off.

[DanTMWTMP]

ok..

LET'S SAY YOU HAVE A SKATEBOARD. you push yourself on NORMAL GROUND to go really really fast. up ahead, is about 10 feet of conveyor belt. No longer do you have force applied, except for the one you gave to the skateboard. Given some people's faulty logic here, the skateboard is going to suddently stop after you reach the conveyor belt omg!!!!11!111!1.

 

[loup garou]

Couldn't this be rudimentarily demonstrated by a toy plane suspended from a string? If you start the engine, the plane will fly (in circles, of course, but that's another lesson).

 

[cKGunslinger]

Originally posted by: deathkoba
There IS forward momentum given any level of engine power applied even if the plane appeared to be still or even moving backwards. Am I incorrect here?

And if there is forward momentum, then air is moving over the wings and there is lift. Why is your stance now the exact opposite of you original statement?

 

[Kenazo]

Originally posted by: DanTMWTMP
ok..

LET'S SAY YOU HAVE A SKATEBOARD. you push yourself on NORMAL GROUND to go really really fast. up ahead, is about 10 feet of conveyor belt. No longer do you have force applied, except for the one you gave to the skateboard. Given some people's faulty logic here, the skateboard is going to suddently stop after you reach the conveyor belt omg!!!!11!111!1.

Of course it won't, but that's where the impossibility of the scenario in the OP comes in.... The conveyer is going to just keep accelerating at exactly the same rate as the wheels, until both of their speeds is infinity. It's impossible to have forward motion unless the wheels will be skidding across the surface of the conveyer.

 

[thirdlegstump]

Originally posted by: cKGunslinger

Originally posted by: deathkoba
There IS forward momentum given any level of engine power applied even if the plane appeared to be still or even moving backwards. Am I incorrect here?

And if there is forward momentum, then air is moving over the wings and there is lift. Why is your stance now the exact opposite of you original statement?

Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

Why is this so difficult to understand? To stay stationary while there is a reverse change in forward motion (the conveyor belt factor), it requires equilibrium forward momentum (created by some engine power) which does not create any airflow over the airfoil in the case where the engine is located in the back. Only when there is further forward momentum applied (more engine power), will there be a change in position creating airflow. It's not like there's a giant hand or something keeping the plane in place to counter the conveyor belt. It is a major factor while the plane is still on the ground.

But the question does not state other factors that defines several key factors such as wind direction and speed, MSL altitude, barometric pressure, type of aircraft, type of engine, speed of conveyor belt, load weight and balance, fuel etc.

Therefore it's impossible to answer this question.

For all we care, the engine could be at full power while this whole event is happening at 50,000' MSL on a Cessna 152 while the converyor belt is moving at 150MPH and weather reporting low air pressure. That plane would barely move it at all.

Get my point? Depending on certain circumstances, the plane can take off or not.

 

[AbAbber2k]

Originally posted by: 91TTZ
If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

This seems to be the best and most simply put explanation that I've seen. The only question is... is there an upper limit on the rotational speed of the wheels before they become mechanically unsound? If the wheels are destroyed before they get off the ground you go nose down in the dirt and then the plane DOESN'T take off.

 

[Glavinsolo]

Cars and planes don't work the same way.

 

[arcenite]

Originally posted by: Glavinsolo
Cars and planes don't work the same way.

 

[arcenite]

Originally posted by: AbAbber2k

Originally posted by: 91TTZ
If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

This seems to be the best and most simply put explanation that I've seen. The only question is... is there an upper limit on the rotational speed of the wheels before they become mechanically unsound? If the wheels are destroyed before they get off the ground you go nose down in the dirt and then the plane DOESN'T take off.

Wheels will only spin so fast before they will be spinning slower than the ground and create friction and start smoking.. much like doing a burn out.

 

[NanoStuff]

Originally posted by: AbAbber2k

Originally posted by: 91TTZ
If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

This seems to be the best and most simply put explanation that I've seen. The only question is... is there an upper limit on the rotational speed of the wheels before they become mechanically unsound? If the wheels are destroyed before they get off the ground you go nose down in the dirt and then the plane DOESN'T take off.

It's simple, no doubt about it, but it's incorrect. If the belt is moving backwards at 200mph the passengers on that plane are gonna be pretty damn disappointed.

 

[AbAbber2k]

Originally posted by: arcenite

Originally posted by: AbAbber2k

Originally posted by: 91TTZ
If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

This seems to be the best and most simply put explanation that I've seen. The only question is... is there an upper limit on the rotational speed of the wheels before they become mechanically unsound? If the wheels are destroyed before they get off the ground you go nose down in the dirt and then the plane DOESN'T take off.

Wheels will only spin so fast before they will be spinning slower than the ground and create friction and start smoking.. much like doing a burn out.

That's my point... couldn't that friction have extremely adverse effects on the wheel's structure? It can't spin fast enough but you're pushing it any which means sheer forces are being applied. Probably lose tire tread initially, but after that... the plane is f*cked. Granted I'd be willing to believe the plane would already be in the air at this point. But it seems like something to consider.

 

[jagec]

Originally posted by: deathkoba
There IS forward momentum given any level of engine power applied even if the plane appeared to be still or even moving backwards. Am I incorrect here?

Nope. Momentum is related to mass and speed, and nothing else. If the plane is stationary with respect to the ground, then it has zero momentum with respect to the ground.

 

[cKGunslinger]

Originally posted by: deathkoba
Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

"You keep using that word. I do not think it means what you think it means."

 

[thirdlegstump]

Originally posted by: AbAbber2k

Originally posted by: 91TTZ
If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

This seems to be the best and most simply put explanation that I've seen. The only question is... is there an upper limit on the rotational speed of the wheels before they become mechanically unsound? If the wheels are destroyed before they get off the ground you go nose down in the dirt and then the plane DOESN'T take off.

Oh boy here we go again :roll:

 

[thirdlegstump]

Originally posted by: cKGunslinger

Originally posted by: deathkoba
Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

"You keep using that word. I do not think it means what you think it means."

At this point I will give up. You're right, I'm wrong. I'm going to go dinner with a bunch of women tonight. Care to join?

 

[cKGunslinger]

Originally posted by: deathkoba

Originally posted by: cKGunslinger

Originally posted by: deathkoba
Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

"You keep using that word. I do not think it means what you think it means."

At this point I will give up. You're right, I'm wrong. I'm going to go dinner with a bunch of women tonight. Care to join?

LOL. No, I have plans with my wife and kids. Once again, you fail. :laugh:

 

[AbAbber2k]

Originally posted by: deathkoba

Originally posted by: cKGunslinger

Originally posted by: deathkoba
Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

"You keep using that word. I do not think it means what you think it means."

At this point I will give up. You're right, I'm wrong. I'm going to go dinner with a bunch of women tonight. Care to join?

Are you saying that if the women are ON the plane it won't take off?

 

[Rainsford]

It will take off, and I'm ashamed to say I said no in the first thead. You know what they say about Democracy though...the best argument against it is a five minute conversation with the average voter. This thread is certainly proving them right

 

[JujuFish]

I'm disappointed in about 35% of AT.

 

[thirdlegstump]

Originally posted by: cKGunslinger

Originally posted by: deathkoba

Originally posted by: cKGunslinger

Originally posted by: deathkoba
Because forward momentum doesn't necessarily equal actual change in position given the conveyor belt factor. The plane already requires forward momentum just to stay stationary. I have never deviated from my original stance.

"You keep using that word. I do not think it means what you think it means."

At this point I will give up. You're right, I'm wrong. I'm going to go dinner with a bunch of women tonight. Care to join?

LOL. No, I have plans with my wife and kids. Once again, you fail. :laugh:

Nah I didn't fail. I'm just busy with other things. I COULD choose to go on and on with you guys but...sorry : )

 

[FusionKnight]

Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong

FK

 

[loup garou]

Originally posted by: loup garou
Couldn't this be rudimentarily demonstrated by a toy plane suspended from a string? If you start the engine, the plane will fly (in circles, of course, but that's another lesson).

Anyone?

 

[thirdlegstump]

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong

FK

Yes you're correct. I don't understand why these so called physics geniuses can't figure out such a simple thing. It's like OMG, a plane's wheels will move without any power applied! It will if it were on a hill.

 

[JujuFish]

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong

FK

Right there.

 

[ultimatebob]

This sounds like a Mythbusters episode in the making