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re: Can this 747 take off?
Posted on 4/10/24 at 7:31 pm to AUFANATL
Posted on 4/10/24 at 7:31 pm to AUFANATL
quote:
The treadmill plane doesn't work because the wings remain in the same place rather than cutting through air thus you get no lift.
Exactly
quote:
The reason they de-ice a plane's wings in wintery weather is because the air molecules will "slide" or "shimmer" off an icy surface rather than form a natural lift pocket and in that moment you are riding in a missile, not a plane. See - several famous plane crashes.
More intricate than that
0
Posted on 4/10/24 at 7:37 pm to Street Hawk
NO what a stupid question 
Posted on 4/10/24 at 7:39 pm to Street Hawk
Only if it reaches 88 mph and gets back to 1985.
Posted on 4/10/24 at 7:46 pm to SaintEB
quote:
But the wheels are stated to be moving at the same speed as the treadmill. Thus, the engines are matching the speed of the treadmill which means the plane is not moving.
And what, pray tell, is the mechanism connecting the engine output to the wheels on such a tight, 1:1 basis?
Posted on 4/10/24 at 7:53 pm to LNCHBOX
quote:
Somehow I knew something dumb was coming when I saw you were the most recent reply.
Yet, you still can’t answer the stupid hypothetical in the OP
Posted on 4/10/24 at 7:59 pm to Street Hawk
Who needs to teach math, science and common sense? Not us.. BLM, lbctq, antiqua power...
the wheels on the plane go round and round...... Everybody buy the pilot a drink.
the wheels on the plane go round and round...... Everybody buy the pilot a drink.
This post was edited on 4/10/24 at 8:02 pm
Posted on 4/10/24 at 8:07 pm to Volvagia
It’s even simpler than that. The speed of the wheels are irrelevant. The purpose of the wheel is to reduce resistance, not produce thrust. Nobody has ever said a plane didn’t get off the ground because the wheels didn’t spin fast enough.
Go ahead and double your hypothetical treadmill speed, the plane isn’t going backwards.
This is as silly as the hypothetical about the plane flying faster than sound …can the guy in front of you hear you speak?
Go ahead and double your hypothetical treadmill speed, the plane isn’t going backwards.
This is as silly as the hypothetical about the plane flying faster than sound …can the guy in front of you hear you speak?
Posted on 4/10/24 at 8:32 pm to lsuconnman
quote:
Go ahead and double your hypothetical treadmill speed, the plane isn’t going backwards.
Nobody thinks that… however, the aircraft still isn’t going forward in that scenario either, so it ain’t launching due to lack of air over and under the wings.
Posted on 4/10/24 at 8:40 pm to lsuconnman
quote:
It contains a basic ambiguity, and people resolve it one of a couple different ways. The tricky thing is, each group thinks the other is making a very simple physics mistake. So you get two groups each condescendingly explaining basic physics and math to the other.
Well, as I see it, there are three possible interpretations. Let’s consider each one based on this diagram:
quote:
1. vB=vC: The belt always moves at the same speed as the bottom of the wheel. This is always true if the wheels aren’t sliding, and could simply describe a treadmill with no motor. I haven’t seen many people subscribe to this interpretation.
2. vC=vW: That is, if the axle is moving forward (relative to the ground, not the treadmill) at 5 m/s, the treadmill moves backward at 5 m/s. This is physically plausible. All it means is that the wheels will spin twice as fast as normal, but that won’t stop the plane from taking off. People who subscribe to this interpretation tend to assume the people who disagree with them think airplanes are powered by their wheels.
3. vC=vW+vB: What if we hook up a speedometer to the wheel, and make the treadmill spin backward as fast as the speedometer says the plane is going forward? Then the “speedometer speed” would be vW+vB — the relative speed of the wheel over the treadmill. This is, for example, how a car-on–a-treadmill setup would work. This is the assumption that most of the ‘stationary plane’ people subscribe to. The problem with this is that it’s an ill-defined system. For non-slip tires, vB=vC. So vC=vW+vC. If we make vW positive, there is no value vC can take to make the equation true. (For those stubbornly clinging to vestiges of reality, in a system where the treadmill responds via a PID controller, the result would be the treadmill quickly spinning up to infinity.) So, in this system, the plane cannot have a nonzero speed. (We’ll call this the “JetBlue” scenario.)
But if we push with the engines, what happens? The terms of the problem tell us that the plane cannot have a nonzero speed, but there’s no physical mechanism that would plausibly make this happen. The treadmill could spin the wheels, but the acceleration would destroy them before it stopped the plane. The problem is basically asking “what happens if you take a plane that can’t move and move it?” It might intrigue literary critics, but it’s a poor physics question.
So, people who go with interpretation #3 notice immediately that the plane cannot move and keep trying to condescendingly explain to the #2 crowd that nothing they say changes the basic facts of the problem. The #2 crowd is busy explaining to the #3 crowd that planes aren’t driven by their wheels. Of course, this being the internet, there’s also a #4 crowd loudly arguing that even if the plane was able to move, it couldn’t have been what hit the Pentagon.
XKCD - The Goddamn Airplane on the Treadmill
This post was edited on 4/10/24 at 8:42 pm
Posted on 4/10/24 at 8:57 pm to Street Hawk
No because the airflow around the wings remains the same thus not creating lift
Posted on 4/10/24 at 9:19 pm to Street Hawk
It's shocking to me that anyone says yes to this.
Posted on 4/10/24 at 9:21 pm to DavidTheGnome
Thank you. A plane stationary, no matter if the hypothetical treadmill was going the speed of light, can’t take off because of Bernoulli's law.
It clearly says the treadmill goes as fast as the wheels. So no matter how much throttle the pilot applies, the plane stays stationary.
And to think that some assholes downvoted me on this.
The air on top of the wing has to be going faster than the air below the wing- hence why a wing is shaped like it is. This creates lower pressure above the wing and then takeoff.
Thrust doesn’t make you fly assholes. Low pressure above a wing does.
It’s why a hang glider works.
It clearly says the treadmill goes as fast as the wheels. So no matter how much throttle the pilot applies, the plane stays stationary.
And to think that some assholes downvoted me on this.
The air on top of the wing has to be going faster than the air below the wing- hence why a wing is shaped like it is. This creates lower pressure above the wing and then takeoff.
Thrust doesn’t make you fly assholes. Low pressure above a wing does.
It’s why a hang glider works.
This post was edited on 4/10/24 at 9:25 pm
Posted on 4/10/24 at 9:38 pm to BottomlandBrew
quote:
The treadmill could spin the wheels, but the acceleration would destroy them before it stopped the plane. The problem is basically asking “what happens if you take a plane that can’t move and move it?”
I was onboard until I saw the final paragraph. Of all the possibilities, the only absolute is that Pirelli made the tires?
If the treadmill is reversed does that mean a plane that’s landing cannot stop?
Posted on 4/10/24 at 10:21 pm to Street Hawk
If there isn’t enough air flowing over the wings for them to create lift then no.
The only way that’s happening is the engines have to create suitable thrust or a giant-arse fan blowing enough air at it.
The only way that’s happening is the engines have to create suitable thrust or a giant-arse fan blowing enough air at it.
Posted on 4/10/24 at 10:26 pm to tigeraddict
quote:
There is no wind blowing over the wings. No lift. This is why an aircraft carrier turns into the wind to launch. Free wind over the wings
I've never seen an aircraft carrier with wings. Much less one take off in flight.
Posted on 4/10/24 at 10:27 pm to Street Hawk
It's been twenty years since I have seen this posted on the internet. Well done.
Posted on 4/10/24 at 10:48 pm to Street Hawk
Posted on 4/10/24 at 10:54 pm to AUFANATL
quote:
…aerodynamical…
Not a word. And, plane go up.
This post was edited on 4/10/24 at 11:00 pm
Posted on 4/10/24 at 10:56 pm to subMOA
quote:
It clearly says the treadmill goes as fast as the wheels. So no matter how much throttle the pilot applies, the plane stays stationary.
I think we would all agree that a plane could fly at a constant speed 10ft above a treadmill moving in an opposite direction but equal speed. The plane could even chose to accelerate if it wanted to.
Why would lowering free-spinning landing gear from the same plane over the same treadmill prevent it from continuing to fly or even accelerating?
This post was edited on 4/10/24 at 10:58 pm
Posted on 4/10/24 at 11:02 pm to subMOA
quote:
clearly says the treadmill goes as fast as the wheels. So no matter how much throttle the pilot applies, the plane stays stationary.
If you held a hot wheels car on a treadmill do you think you could move the car forward with your hand? No matter how fast the treadmill was going it would take very little force to move the car forward with just your hand.
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