Would it take off?
I think so. It also seems like it would crash into the front of treadmill as soon as it did. I don't know shit about physics though.
>>7992852
Is air passing rapidly over the wings? Then no
>>7992857
What if there was a fan at the front of the treadmill?
>>7992857
The wheels don't drive the plane, the wheels spin rate is proportional to the air speed velocity and the radius of the wheels plus whatever additional speed the treadmill operates at.
air speed is determined by the engines
the wheels spin at a rate proportional to the air speed plus the speed of the treadmill
the speed of the treadmill is unbound
>>7992869
Then yes, if the fan blows hard enough. But then you dont need the treadmill
>>7992873
If you are on a treadmill, there is no airspeed. To get lift you need air to pass over the wings, if the plane isnt moving, that wont happen
>>7992876
Yes you would still need the treadmill or you wouldn't be able to fire up the turbines without the plane crashing into the fan.
>>7992879
Jet turbines pass air under the wings and drag air from over them..
>>7992879
>If you are on a treadmill, there is no airspeed
exactly, which is why you have to run, you are more than welcome to strap a jet booster pack on which will give you air speed to prove my point, be my guest
>>7992886
Jet propulsion actually converts static air on the intake side in to high velocity air via combustion of jet fuel, the energy exerted out the exhaust of a jet engine causes a Newtonian reaction force on the plane itself which propels it forward
>>7992887
So if a plane is on a treadmill, it isnt moving forward, which means no airspeed and no lift, no matter how fast the wheels are turning
>>7992893
Then it would crash as soon as it took off and flew above the fan.
What if it were a propeller plane like a wright flyer. Would this make a difference?
>>7992896
as soon as the engines kick on there is a forward force imparted on the plane from the engines. F=ma, there is acceleration, acceleration over time is velocity. The wheels spin freely at a rate that is proportional to the air speed and an arbitrary treadmill speed.
>>7992896
Which of course leads to the obvious point that putting a plane on a treadmill wouldnt stop it moving forward, so the whole scenario is stupid anyway
I can't believe this problem is still going on.
It won't take off until you turn the treadmill off. It's the same principle as revving your engine before gunning it. You ramp up the engine while not in gear then when you throw it into first you take off like a bat out of hell.
Same thign for the plane: the engines get up to speed and as soon as the treadmill stops (resists motion) the plane will be at nearly full speed. This is actually more impactful for the plane as it doesn't have to worry about gear ratios like a car does.
If we could build a big enough treadmill then this would be a perfect VTOL solution.
>>7992908
listen you have no idea what you are talking about first of all it will take off so you are wrong you dont konw what you are talking about second is that a plane is not like a car when you rev the engine are you kidding me then when you ar ein gear is completely different than when you are in a plane because a plane has engines and etc plus finally you cannot stop
listen you have no idea what you are talking about first of all it will take off so you are wrong you dont konw what you are talking about second is that a
plane is not like a car when you rev the engine are you kidding me then when you ar ein gear is completely different than when you are in a plane because a plane has engines and etc plus finally you cannot stop
listen you have no idea what you are talking about first of all it will take off so you are wrong you dont konw what you are talking about second is that a plane is not like a car when you rev the engine are you kidding me then
when you ar ein gear is completely different than when you are in a plane because a plane has engines and etc plus finally you cannot stop
>>7992936
Why would the plane take off if its not moving forward? If it is moving forward, whats the point of the treadmill?
>>7992852
They already did it though
https://www.youtube.com/watch?v=01Q83yxdDaI
>>7992964
the actual ending
https://www.youtube.com/watch?v=YORCk1BN7QY
>>7992852
No, it would go backwards and fall off the treadmill.
If it were a real plane on a mega huge treadmill, long enough for a runway, and the plane was fueled and using its turbines, yes, since it would be the same thing as a plane taking off on the opposite direction Earth is spinning.
>>7992968
>>7992964
The real problem is that the original image used a non-powered toy plane and the treadmill was the power source for the plane's movement. Hence just falling off the back of the treadmill. A plane with its own thrust always takes off.
>>7992941
The plane would be moving forward, The point it to fuck with stupid people who don't know how planes work.
>>7992852
>people say it doesnt take off
>planes cant ever take off against the rotation of the earth
lol /sci/
it would fall of the tread then move until it reaches takeoff speed
assuming it doesn't crash into those poles
https://blog.xkcd.com/2008/09/09/the-goddamn-airplane-on-the-goddamn-treadmill/
TLTR: "...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."
>>7992852
Let v1 = the airspeed at which the plane achieves flight
Let v2 = the maximum airspeed under full power in calm air level flight
Let v3 = the maximum groundspeed of the plane (i.e. wheel friction limited)
None of these are known/stated in the problem,
and would be the minimum(?) information needed to answer the question.
>>7992896
>So if a plane is on a treadmill, it isnt moving forward
But this is wrong. It is moving forward. Despite the treadmill moving opposite to its intended motion, it's not pushing off the ground like a runner or car would do. Propellers are pushing off the air around it. As long as the wheels are free spinning, it doesn't matter what the treadmill is doing.
How fast does the threadmill go?
Fast enough that it causes so much friction for the wheels that the plane experiences no acceleration/stands still?
Then no.
If the plane can still move forward then it will just take off.
They have done a mythbusters episode where a single turbo prop engine was able to take off the runway with a tarp as the treadmill.
The exact forces were not specified, but the action of lift is generated by relative airspeed moving along the wing/lifting surfaces of an aircraft.
The aircraft takes off because of the reactive forces of it's propulsion, allowing it it to gain inertia while the wheels spin freely. The wheels don't drive the plane forward.
Where is this relative airspeed coming from? Well if we consider that the airplane will always overcome friction from the ground, and maintain it's momentum, then it will be able to outrun the treadmill giving it enough forward velocity to take off.
In a hypothetical zero friction environment (including a jet pack to maintain initial position) you could flick a mass of a mega-jillion-ziilion kilograms and have it move away from you, albeit really slowly.
>>7992852
Yes it will take off.
2006 CALLED IT WANTS THE PLANE AND THE TREADMILL BACK
>>>/b/ sucks now, [s4s] is the nicest board.
All this BS semantics and pretty little physics words aside, this isn't rocket science. Lift is generated by an increase of air pressure below the wings, and decrease above. This requires air current.
While it's true that the turbines generate their own air current, I can fucking promise you lot that a lot of that air current comes from the actual motion of the plane through the air.
So I seriously doubt your standard turbines would even be physically capable of producing enough air current on their own, to lift the plane up while stationary, without breaking. And even if they were, it would be highly energy inefficient compared to allowing the plane to move forward without the treadmill and build a natural air current around the wings.
This is common sense, no physics needed.
>>7992895
>a Newtonian reaction force
What are you, 15? Who are you trying to impress?
>>7992852
no, wingspan too big
>>7992873
>air speed is determined by the engines
thrust is determined by the engines, air speed is determined by the relative velocity of the plane. change in position of a plane on a treadmill is 0. no change in position = no velocity = no lift
the wheels have angular velocity but no linear velocity.
How is /sci/ this retarded. no the plane won't take off because there is no air passing over the wings. Yes jets can fire static but that's not what lifts a plane upwards, this should be obvious.
>>7993519
The treadmill cant stop the plane moving forward no matter how fast it runs
>>7993544
>This problem usually assumes there is enough treadmill to do a take off run.
So what's the treadmill there for? Just take a normal takeoff then. Having enough to do that, defeats the entire purpose of the treadmill idea, so I seriously doubt this is the case.
>>7992856
>>7993438
>what is a metaphor?
Jesus. For a science board, this place features a larger percentage of idiots than I see in the general populace. And that's a frigging huge insult btw. Literally almost everyone I know IRL has this figured out in a few seconds flat.
See this post:
>>7993363
>>7993554
>So what's the treadmill there for?
Apparently its just to make people think that somehow a treadmill can keep a plane stationary. In real life the plane will take off
>>7992936
Wew lad
>>7993554
> So what's the treadmill there for?
Presumably to impart some condition that may result in the plane not being able to take off.
>>7993557
>In real life the plane will take off
You have no proof of that.
>>7993560
So this entire debate comes to semantics and misunderstandings. You're saying it's a trick question?
One group assumes that the treadmill is barely the size of the plane, and the takeoff needs to take place vertically, relatively speaking, on the air just above the treadmill.
In short, can a plane take off if with the lift generated by its jets / propellers alone, if something were to keep it stationary?
The other assumes the treadmill is as long as any runway, where the only question really will be the friction between the treadmill and the wheels, as the jets will propel the plane forward regardless of the speed of the treadmill.
Where's the debate then? Both are right:
In the first scenario, NO, the plane cannot take vertically with jets alone. They don't have the power to generate the necessary lift without the air current that comes from physically moving the plane forward and generate enough air current on the wings.
In the second scenario, yes, assuming the treadmill isn't moving fast enough to blow up the tyres and crash the plane, the jets will absolutely propel the plane forward and eventually enable a takeoff regardless of the treadmill.
So there's no debate, not on those terms. The real questions then are these: is the treadmill long enough to function as a runway? And is the friction and the speed of the treadmill low enough to not blow up the tyres before the takeoff?
>>7992968
>>7992964
What a bunch of fucking shitheads. The whole point was that the original used a toy, not even a powered toy, just a fucking toy plane. What happens? The treadmill shoots the plane off the back. Nothing more.
>>7993597
>yes, assuming the treadmill isn't moving fast enough to blow up the tyres and crash the plane, the jets will absolutely propel the plane forward and eventually enable a takeoff regardless of the treadmill
Why must the tires or wheels fail to keep the plane from taking off ?
It seems the conveyor belt might impart enough backwards force to just barely keep the plane from reaching it's minimum takeoff speed. In this scenario the plane would eventually fall off the front end of the belt (and not takeoff) but without wheel failure being the cause.
>>7993565
Its been done, the plane took off
>>7993597
Pretty much, all that happens is people argue over how they have interpreted the question, without ever pointing out there are different interpretations.
The first time I saw it I assumed the plane was never turned on, and the question was asking whether running a treadmill under the plane would somehow make it take off
>>7995479
> Its been done, the plane took off
No it has not been done.
A real world passenger jet on a large *unlimited*
speed conveyor belt has not been built.
>>7995464
The amount of friction through the wheel axles is tiny compared to the thrust from the engines. If the treadmill was actually going fast enough to hold the plane below take-off speed, then something would very quickly fail on the plane.
>>7995499
>*unlimited* speed conveyor belt
If you invoke magic in the question then any answer is equally valid.
>>7995507
> The amount of friction through the wheel axles is tiny compared to the thrust from the engines
You mean like in a car, where you can brake the vehicle from 100 mph to a full stop without damaging the wheels ?
>>7995499
Tell me precisely how a conveyor betl moving at any speed can stop a plane moving forward under its own power?
>>7995507
> If you invoke magic in the question then any answer is equally valid.
Not magic. Impractical maybe.
Physics often asks questions that assume
a theoretical limit or value more unrealistic than can be inferred from the OP's question.
>>7995519
no, he means like in a plane, where you could exert enough friction to destroy the wheels and the plane doesn't really care because wheels aren't connected to the engine and aren't powered
>>7995521
> Tell me precisely how a conveyor belt moving at any speed can stop a plane moving forward under its own power
Precisely through the friction of the tires
meeting the moving belt and attendant effects, a backwards retarding force is generated that will prevent the plane moving forward relative to the non-moving part of the conveyor belt.
It's a rather simple concept.
>>7995557
So then the wheels are destroyed and the plane crashes. And if the wheels (and plane) are indestructible then what is the point of even asking the question?
>>7995548
> the plane doesn't really care because wheels aren't connected to the engine and aren't powered
That's the problem today. Planes don't really care about their wheels. In the days past they really cared.
Kek
>>7993363
The F4s wings did nothing for lift, it was all engine hence the name 'the flying brick'. A similar moniker will eventually be bestowed upon the JSF whose wings are also painted on
>>7995596
>>7995563
> what is the point of even asking the question?
What is the point of going to the 4chan website ?
>>7995634
Interesting discussion. Magical planes on magical treadmills isnt an interesting discussion though. Real planes on actual treadmills subject to real physics might be interesting
>>7995572
> This is why,for example, the airplane/treadmill problem is a banned topic...
I'm not sure these topics ever need to be completely banned, but the OP should clarify which variant of the problem they want to discuss because there is already enough ambiguity in these sorts of questions.
>>7995639
>>Magical planes on magical treadmills...
There are all kinds of real planes, so not sure what you mean.
As to treadmills, you seem to be making an engineering assessment, that like a slow big
treadmill might be OK, but there exists a speed
s1 such that if the treadmill RPM needed is beyond s1 then you may argue physics on the basis of your smug scorn.
>>7992857
this
quit being retarded everyone
>>7995719
the plane is going to go forward no matter what, and it's going to go forward fast. that's going to mean air and liftoff
you can't stop the plane for moving no matter what you do to the wheels. do the force diagram, it would quickly speed to infinity
>>7995687
In real life a treadmill cant stop a plane moving forward
>>7995807
*without destroying the plane
>>7992857
>Is air passing rapidly over the wings?
The engine cause the air to pass rapidly over the wrings so yes
>>7995899
Only if the plane is moving forward
>>7995907
>Only if the plane is moving forward
Which is the job of the engines, not the wheels.
Good work, now you understand what a plane is.
>>7995937
Yes, but the engines can be running and the plane not move forward, like if there was something in front of the plane, or there was a treadmill underneath running backwards extremely fast
>>7995955
It would need to produce more friction than the engines produce thrust. Meaning it would need to spin fucking quick since wheels are designed to minimise friction.
If the treadmill has infinite speed, the plane won't move. If the treadmill is limited to the planes max speed, the plane will move forward slower, but fast enough to take off eventually.
>>7995997
It doesnt need infinite speed, just extremely high, but yes
>>7992852
If the treatmill moves at the same speed as the plane then yes but only if the treadmill is backwards because else the plane would crash into the mill
>>7992852
76 replies.
Ah /sci/, the place where free will can't exist, negative numbers are an elaborate hoax, gravity doesn't real and the Earth is flat.
Of fucking course it takes off (treadmill length permitting).
Would it take off?
Should it take off?
It depends when the treadmill is turned on.
If it's on before the plane's engines turn on, the plane rolls off the back and you've probably fucked the plane.
If the engines are on before the treadmill, the plane crashes into the front of the treadmill and you've probably fucked the plane.
