Plane on a Conveyor Belt Controversy
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- čas přidán 5. 06. 2024
- Tested member Jordon Freeman wanted to know, "Do you think the controversy caused by 'plane on a conveyor belt' will ever end?" Oh boy. Here's Adam's answer, and thank you, Jordon, for your support! Join this channel to support Tested and get access to perks, like asking Adam a question:
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keep up the great work 👍🏻
If a car goes fast enough on a conveyor belt it too will take off 🤣
The car also moves forward, given the precise phrasing. If it didn't, the conveyor wouldn't be moving either (that said, the speedometer would be showing a speed twice as fast as it's actually going)
While I never doubted the plane would take off just fine with the problem as stated I do still find myself thinking there is some speed the treadmill could run that would prevent takeoff but it would be considerably higher than the plane's takeoff speed. My logic here is that the friction between the plane's wheels and the surface is transferred to the airframe and thus does bleed off some energy. The plane's engine does have a maximum thrust force it can produce if you could produce enough friction that the force completely countered the maximum thrust you could prevent it from taking off. Granted attempting this experiment in practice would almost certainly result in catastrophic failure of the tires and wheel bearings since they are most definitely not engineered to sink 100% of the engine's maximum power output single-handedly. I'd bet on this experiment at a minimum resulting in autoignition of the tires and bearing lubricant, though probably the bearings would become severely deformed white-hot metal would along with much of the wheel itself. Those parts are much smaller and far less well cooled than the leading edges of the body that usually dissipate most of the power through air drag at higher power settings during normal operation.
Im not familiar with this episode but I am surprised it would cause that much controversy. Even the pilot thinking it wouldnt work blows my mind. Unless the wheels are driving the forward motion a conveyor belt isn't going to do anything but make the wheels spin really fast, meanwhile the pane continues to move forward just as it would normally.
It surprises me that it's not obvious to everyone.
A good analogy would be roller-skating on a treadmill while holding a rope attached to the wall in front of you. No matter how fast the treadmill moves, if you hold on to the rope you'll stay still. And if you pull on the rope you can still drag yourself forward. The rope bolted to the wall represents the stationary air around the plane which the propeller uses to 'pull' the plane forward.
That's a really good explanation!
I think most people don't realize how slow a plane's speed is needed to take off versus its max speed can be. As long as the plane has power to hold still on the belt and has more power to read takeoff speed, it will take off
@@mikeuk666 The wheels can't make the plane stuck, they just spin. If the plane moves forward 1 m/s and the belt moves back 1 m/s, the plane still moves forward and the wheels just end up spinning at 2 m/s.
That's a smart analogy!
@@danno1111 ...so you're saying if the plane wheels spin faster than the conveyor belt it takes off. While true, it breaks the entire premise of the question.
1:30 Jamie: "Why would we test that. It's stupid".
This is why I always liked Jamie. He openly stated his opinion
And he was right
I mean, the plane's jet engines don't push against the conveyer belt. It pushes against the air.
@@macavitythemysterycat actually it doesn't push against the air, it simply fires the air back hard enough to move itself forward. that's the same argument that flat earthers put up to say that rocket engines wouldn't work in space, because they think that the rocket exhaust pushes against the air to move the rocket forward, however that has nothing to do with it.
A propeller is just a wing turning around a fixed point. The blade moving through the air creates a low pressure on one side and a high pressure on the other side. This then sucks the wing from the high to the low pressure side. The blade is attached to the engine and the airframe. This causes forward movement as the plane is sucked through the relative air. Same for a jet engine. There is a small amount of mechanical movement created by the actual interaction of the air molecules with the mechanical components but most of the action is throught a difference in air pressure. A rocket works by throwing mass in a driection. There is an opposite but equal reaction in an opposite direction. That is why a propeller does not work in a vacuum but a rocket does. Two completely different principles.
@@alexanderenericavanwyk9909 nah lol I'm pretty sure a propeller works by pushing air in one direction, not by causing a difference in pressure. It's literally the same thing as a rocket engine, but with internal combustion powering moving parts rather than being expulsed at high speed. And while there may be a pressure difference between the 2 sides of the propeller, it's because of the air being moved around.
Love that Adam's take on the confusion is "this is fantastic" instead of "people are bad".
That's the real lesson of this.
Something you didn't touch on but I think is important is that the airplane's wheels spin freely. If the runway is moving, the wheels will spin faster, but it would have to move fast enough to actually break the wheels to the point of locking up for the plane to not take off. A fast enough conveyor belt would stop a plane from takeoff, but not at all for the reasons it would stop a car. It would be more like a belt sander. XD
The question has always specified that the runway "matches the speed of the wheels" so the runway doesn't simply move fast enough to damage the wheels. The problem is that "matches the speed of the wheels" is ambiguous. The wheels as a whole will be moving forward at the same speed as the airplane, but the relative speed of the wheels where they contact the runway is the speed of the plane + the opposing speed of the runway. In that scenario the wheels have to speed up to infinity the instant the plane starts to move.
@@suedenim9208 ah but you see, spinning up the wheels via belt actually imparts force on the rest of the plane as well, due to their inertia, so the belt does not need to spin up to infinity instantly. i can do some math to calculate the acceleration of the belt in order to counteract the thrust of the plane but id rather not go through the trouble.
@@aerbon You know the question isn't about real life, right? It's a hypothetical physics question , so the conveyor that's as wide and long as a runway and capable of exactly matching the speed of the wheels exists in an imaginary place where wheel friction and inertia aren't part of the question.
@@suedenim9208 It is exactly because this is an imaginary scenario that i bring up wheel inertia. A real conveyor would never be able to accelerate forever.
I just like to point out that there is a reasonable way the conveyor can affect the plane. enough so that i believe if i had a high enough budget for a conveyor i could stop a plane from accelerating for a few seconds.
@@aerbon I think in a hypothetical scenario where there is no friction, it would also be assumed that the wheels are massless, meaning there wouldn't be any inertia.
It's almost like people are rejecting your reality and substituting their own...
I see what you did there.
It’s the same reality. One side understands how the plane actually works, the other has a theory that’s valid, but that valid theory is for the wrong problem.
I see what ya did there, and I approve!
Nice work.
@@triforcelink Thank you for ignoring the joke and writing an explanation to a question nobody asked. It's very helpful.
I remember watching that episode, but at the beginning of this video, I thought "of course it won't take-off. if the plane isn't moving forward, there's no air moving over the wings to create lift", but listening to you re-explain the controversy and the reason it works, it was an "a-ha, that makes sense, didn't think of it that way" moment and then remembered the episode. So, even having seen the experiment, my gut reaction was "no, it won't work".
Yes but he only explained how a plane moves forward, not how it moves upward. How does he propellor making it move forward create lift under the wings? I’m just voicing my ignorance not arguing with the result
@@calumryan6328 I am definitely not qualified to explain aerodynamics :)
@@calumryan6328 Once the plane reaches sufficient speed through the air it will take off. So the propeller will generate "air speed" as Jamie explained and that will cause the air flow over the wings to generate the lift for take off.
@@mecklejay7587 No.
@@calumryan6328 lift is generated because of the wings shape which causes a pressure differential to form. So the act of moving forward at a great enough speed would create enough of a pressure difference above and below the wing to allow for take off
My family is from Alaska where small planes are the _only_ way to reliably access large portions of the state year round (we live in the continental US now). This episode was so confusing to us specifically because we weren't sure what was being tested, since of course the tires (without breaks ofc) have zero input on the propulsion of the aircraft. In Alaska small planes are almost as likely to have floats or skis as they are wheels, so the idea of wheeled propulsion being an issue didn't even cross our minds.
Also this episode was part of a larger series of Alaska episodes (moose vs car, specialty Deadliest Catch etc) and my parents recognized several high school and college friends that made it in to Mythbusters and other shows who've gone into various Alaskan bush careers, so thanks to Mythbusters for supporting them!
Guess they dont have conveyor runways either in Alaska. They are very big down south.
@@mokiloke Oh they have plenty in Alaska, we call them "rivers"
@@thecactusman17 holy crap that was witty and on point
With a floatplane, the factors are a bit more involved, as the floats do have significant friction against counterstreaming water, meaning that it takes a more powerful engine to get sufficient airspeed, while also spending energy on creating a wake on the water surface. Sure, it would still take off, unless barely having enough power without the additional resistance.
I'm with Jamie, it's painfully obvious how it works.
The wheels free spin, they will just spin faster on a treadmill.
A seaplane seems like a good way to explain the difference between a car and a plane. You get rid of the wheel confusion and they move forward the same way a regular plane does.
But to add to the confusion seaplanes struggle and many can't take off against a heavy current.
@@irtheLeGiOn Never thought about that.
Just a thought that came to me, but in that situation with strong current...couldn't you just point the nose down current to generate some free headwind and take off easier?
I mean I understand the headwind is going to be almost negligible, but I've never before this second considered the dynamics of a seaplane taking off at the mercy of a strong current.
@@kingtheoden2390it would also be possible, given the surface of a runway not being smooth enough or the airplane heavy enough, or let’s imagine a runway that is not a hard surface, for the wheels of an airplane to be enough of an impediment in the same way to prevent it from taking off.
@@irtheLeGiOn that's just friction. Normally the friction induced by the wheels on an airplane negligible. But if you ran the conveyor belt fast enough, you could actually generate enough friction to prevent the plane from taking off. This would basically mean converting all of the thrust produced by the airplane into heat, all concentrated in the wheels. For the few seconds before the wheel simply explodes because it's spinning hundreds of times faster than designed, the plane would be prevented from going anywhere
@@_FirstLast_ I don't think the issue is current; it's heavy surf which would make the plane bounce up and down and threaten the structural integrity (not to mention the effects on the people inside). In a hypothetical scenario with a wide open and calm body of water, it's not as simple as pointing the nose directly down current, of course. There is also the wind to consider which can reach much higher velocities rendering the current almost negligible. But there's probably a takeoff vector that maximizes the airspeed so that would be the best. But in a real world scenario you're only landing (watering?) the seaplane somewhere if there are interesting things at that location for the passengers or cargo to do, so there will be limitations on the lanes that can be used for a water runway.
To put it simply: All the conveyor belt does is make the plane's tyres spin really fast, which doesn't effect the body of the plane and thus doesn't keep the plane from moving forward and taking of.
Yes that's a really good way of describing it.
I thought that exactly the moment he brought up the topic, but you need to explain further as to the fact the wheels are actually not the thing pushing the plane along. It really does need more explanation for some unfortunately 😄 ignore the wheels, they do notht
Plot twist. The plane has water skids
@@MrEsphoenix & could a plane with water skids take off from a fast moving river?
@@TheFatblob25 Yes, actually. The lift is generated by the aerofoil combined with the engines. The river flow doesn't do much here. The only exception would be if there were all out waves going over the aircraft (disrupting the aerodynamics of the shape of the aircraft) or if the wind was unfavourable. But not the flow of the river itself.
I ADORE how he interrupts himself. It’s like a million Adams jostling for air time.
welcome to a small peak at what true adhd is like
He is approaching the subject matter from different angles to convey a better idea. This makes it more relatable and easy to understand.
@@shanebryant6478 still better than chronic depression
Cmon it can’t be more than 783,000
You and Jamie inspired my kids into the Maker Movement which led to a kickstarter, learning to code, 3D Printing, College and all that sort of self-sufficient nonsense.
Thank you for all you did.
P.S. RIP Lucas the rat!
Working on my GA pilot certification currently and i think of this "myth" with every takeoff. The ground is irrelevant. ☺️ I've always had such respect for Adam and his vocabulary. Thank you Adam for so many years of education and entertainment.
best of luck
HES WRONG.. Cant believe adam doesnt understand the premise of the riddle The conveyor belt (Exactly)matches the speed of the wheels the plane couldn't move forward at all because the acceleration of the belt would be pulling the plane in reverse with the same exact ammount of force its exerting into the air with its engines. if it was exactly matching it the tires would explode before the plane moved forward at all his scenario means the conveyor belt isn't working correctly for the riddle. (The plane could never move forward if the belt is quickly accelerating in reverse with the same force of its forward thrust)
@@tmaxxmm541 No, you are so wrong. Plane is not car.
@@emperorfaiz no, he's not; if the plane cannot move forward because a hypothetical conveyer is precisely matching the speed of the wheels in the opposite direction, and assuming (as Adam mentioned) the absence of a headwind at or above the aircraft's minimum take-off speed, there will be no lift and, consequently, no taking-off. Also, Adam's explanation of what a propeller does makes it abundantly clear he doesn't understand how a propeller actually works. Not once did he mention Bernoulli's Principle and/or what actually creates lift. ANY certificated pilot should arrive at these same conclusions; if not, they should go back to ground school.
Imagine a conveyor belt in the other direction with the wheels fixed so they couldn't spin. Would that plane take of? The wheels are irrelevant unless they are the driving force for takeoff
"The ground speed is irrelevant because airplanes push off the air, not off the ground." seems like a pretty fast explanation to me.
But in order to go forward the wheels must move forward relative to the ground. The question is actually more complicated than either side thinks at first.
@@hautehussey that's *not* true, though. As Adam just explained, the wheels and the ground have a absolutely nothing to do with how the plane propels itself during takeoff.
@@hautehussey yes, it depends on friction coefficients. Theoretically if you could speed up the ground fast enough that through the loss via friction in the wheel components you exert the same drag backwards on the plane as the momentum the plane is building forwards, you should be able to keep it stationary.
But this can't be proven in the real world because a) the amount of force exerted via friction is minuscule, so to make use of it you'd need to accelerate the conveyor belt to speeds that are hard or impossible to manage from an engineering standpoint, and
b) this friction on the wheel system creates thermal dissipation of energy. If you achieve this the wheel bearings would heat up and probably seize and fall pretty quick, as the rpm on the wheels necessary to hold the plane back thorough this friction would be astoundingly high.. in fact maybe the tires on the plane would disintegrate from the rotational force long before the friction in the bearings can destroy them.
@@coredumperror yeah like hautehussey is right that the wheels will be spinning faster BUT that’s not a problem, the wheels will just be spun faster since they’re free-spinning
U also have to take the viscosity of air into account
0:11 “almost exactly 5 years”
Spoken like a true engineer.
officially! lmfao
And if he where a physicist, they'd be spherical years in a vacuum.
This was my favorite myth that you ever did, it was super memorable for some reason (probably because the results completely surprised me, but the explanation made so much sense at the end)
XKCD did an excellent write up on this. The reason there is a debate at all is 100% because the question is ambiguous and people make different assumptions of how the conveyor belt is going to act, not that people don't understand how planes work.
The question itself is a red herring. It makes you think the wheels have something to do with taking off, when really they're completely passive and couldn't care less how fast the ground is moving.
This isn't 100% true. The wheels do matter to a plane on take off. As a plane accelerates, the friction experienced by the wheels increases. It is possible that a plane with very bad wheels and an anemic engine would never be able to take off, because as it approaches takeoff speed, the wheels are relative the conveyor belt, moving twice as fast as normal takeoff. If the friction was high enough, it is possible that the wheels would slow the plane down enough that it can't ever reach take off speed, if under normal conditions it barely could.
This is likely just an edge case, I would imagine most aircraft's wheels would not generate enough friction to prevent a plane from taking off even if they are moving at twice speed as normal, and most aircraft engines have more than enough power to compensate, but it does demonstrate that wheels are not entirely a red herring.
@@albertjordan3249, or, in the case of a 747 (as the question normally references that aircraft specifically), it could come down to the fact that it normally rotates very near to the maximum tire speeds that it can safely handle, and while it may have the power to overcome the added friction from the treadmill in theory, its tires would likely fail before it could attain Vr. Once the tires failed, the friction would increase significantly, and the aircraft would likely come to rest on its engine pods, destroying the engines, and ending its chance at taking off before it reached rotation. This would likely be true if heavy, and would be likely a tight one while light...
@@stephenhalby Yet wheels and tires survive landings, something that exerts many times more friction and forces than take off exerts on them, even with a conveyor belt striving to thwart the planes forward momentum.
@@stephenhalby You're not incorrect, but when talking about a conveyer belt the size of a runway you should accept that the discussion is no longer about practical limitations and more about the basic underlying physical principles.
@@albertjordan3249 Would it only ever get to negative the speed of the plane? I might have had it told to me worded differently but i always saw the treadmill speeding up infinitely to such an extent that the friction would always equal the force coming from the jets and my answer has always been that the bearings would explode and the plane would plop on to it's belly. I'm sure it's never been the conveyer belt "matches" it's speed when I've heard it.
That is sort of insane thinking about it, I guess if the plane needs to go 300mph to take off so long as there's leftover power and the wheels can do 600 to offset the runway you'd be golden. Might still explode the wheels off and plop on to it's belly, no idea how fast planes go and how robust the landing gear is :)
I wish on the Mythbusters episode they'd put a speedometer on the planes wheels. Because what is happening is the plane moves forward at its normal speed but the wheels actually spin twice as fast as in a normal takeoff. That might have been a light bulb moment for a lot of people.
This is the lightbulb moment that actually falsely makes people believe that the plane would take off.
Need to interject here. While the experiment showed that the plane would take off, the experiment itself was fundamentally flawed, and I'll explain why in a few lines. This is not a dig at Adam whatsoever. But in order to answer the question portrayed, the details have to be absolute. No new variables or flawed math, intentional or not.
The wheels and the conveyer belt are the ONLY variables that matter and I'll explain why in a few lines. It's a fundamental physics problem. It does not matter if the wheels and engines are mechanically connected or not. Adam is a great educator, actor, tv host, etc., but he is not a scientist or engineer. It's not a problem of if the plane can reach a speed to take off. Obviously a plane needs ample amount of lift to take off .It's a problem of if the plane will move whatsoever. And the physics of the problem stated does not allow the plane to move.
This is COMPLETELY wrong, and I wish he would just go do more research instead of sticking with his guns in the "my experiment proved it so it cant be wrong." fashion. I grew up watching Myth Busters and absolutely love the show, but experiments do not always provide correct outcome if the variables are not perfect and if external variables are added.
The mode of force, tires vs propeller/engine are irrelevant. The ONLY variables that matter are the wheels and the conveyer belt. It doesn't matter if its a propeller pulling, an engine pushing, the wheels mechanically turning, a person off the conveyer belt pulling, any of that. If you tied an infinitely strong rope to the front of the infinitely strong hull of the airplane and applied an infinite amount of force, you would not be able to move the plane. The only thing that would happen is the wheels and conveyer belt would reach an infinite speed.
This concept is so hard to grasp because it's out of touch with reality. 99% of physics questions taught in classrooms happen in a perfect hypothetical world, and could not exist in the normal world. And if they did, the results would be drastically different. This is one of those questions. There are two main reasons that the experiment that you did were flawed.
1a. It is impossible to instantaneously match the speed of the tarp and the speed of the wheels on the plane.
1b. As the plane tries to take off, the acceleration of the truck needed to accelerate match the planes speed. Going the same speed as the plane is useless. The math does not add up.
2. The tarp that you pulled was also in contact with the ground and not supporting the weight of the plane. Thus, the plane was able to use the ground underneath to help propel itself forward.
It's even impossible to replicate the perfect experiment no matter how much money you throw at the project. So you have to rely on fundamental physics to figure out the problem.
Breaking it down fundamentally.
If the circumference of your tire is 1 meter, as the tire rotates, the conveyer belt moves back 1 meter, matching the speed of the plane's tires instantaneously. In order for the plane to move horizontally, the tires have to rotate. And the tires cannot rotate without the conveyer belt moving the opposite direction the same distance at the same speed.
The issue is that it’s not fulfilling the original question, there’s a bit more nuance. The original question has the belt matching the wheel speed, not the plane’s speed like he says here.
Let’s say plane is moving forward at 1m/s, then the belt is moving back at 1m/s, then the wheels are spinning at 2m/s.
But, now the belt matches the wheel speed, increasing the wheel speed, increasing the belt speed, and so on.
Since the plane *must* move forward, it is impossible to make a conveyor belt match the speed of the wheels, so the premise of the question is impossible
@@expandingsalad786 but that part doesn't matter since the wheels are free spinning it would have no effect on the motion of the plane, so it is a trick question in multiple ways.
@@expandingsalad786 I think that's what makes it so controversial. The question is worded in such a way to make it sound like the conveyer belt would negate the speed of the plane, when in fact the motion of the plane has nothing to do with its wheels.
That's what I was thinking. Could you move the conveyor belt so fast that it could prevent the plane from taking off...in essence creating so much friction on the tires that it overpowers the friction of the air and the propeller?
The problem with the way the question is often put, is that it makes one jump the first consideration, which should be: "How does the plane move to the (stationary to the air) outside observer?". It kind of already implies that the plane stands still, even if it doesn't say it. Once you make that jump there's no way back but to start again.
There is an opposing force. The wheels have friction with the ground. This friction depends on the weight of the plane. So as the plane speed increases , the wheel speed increases , the conveyor speed matches that and the airplane remains stationary relative to the air and ground. It cannot take off.
there are like three parts of this story that are all perfect examples of and/or metaphors for like, *every* misunderstanding on the internet, it's so wild.
What you need to tell people to break them out of the trick of this question is that the plane's wheels are free spinning. All the conveyor belt will do is increase the speed of the wheels spin, but not affect the speed of the plane.
Until the landing gear break off/blowout anyway.
Cool thought, If the treadmill is going faster than the plane, i.e. the plane is going backwards, the plane will still take off
@@briang9471 what? No. The treadmill's speed is irrelevant to the speed of the plane, the treadmill can only effect the speed of the plane's wheels. The plane's forward movement is unaffected, and it takes off like on a normal runway.
@@briang9471 the whole point is that the plane would not ever be going backwards as long as there is a force overcoming the rolling friction of the wheels, which a plane already does to take off on a normal runway, it will continue to move forward. sure, there could be a measurable drag on the plane because of the rolling friction, but it's vastly insignificant compared to the thrust of the aircraft. imagine that the wheels are blocks of ice on teflon or something. If you pull the big sheet of teflon out from under the blocks of ice, they almost wont move, like the tablecloth yanking trick.
*affect
This is WHY "Mythbusters," was such an important show. The actual SCIENCE behind this episode was incredible, and I truly appreciated that you did this!
And yet, in this case, they were (almost) entirely wrong and even after all these years haven't gotten the point.
They were able to put the science into bite sized pieces and explain it and that is the true awesomeness of that show.
Carlos Estrella, except for all the times when they screwed up the science. I always liked the concept of the show, but after watching enough episodes where they claimed to prove or disprove something, but actually did not because their understanding of the science was insufficient, or their experiment methods invalid, I gave up on the show. More recently, when the subject of the show comes up within group my associated who are scientists and/or engineers (I am both), it is always a heated topic, and those who still claim to like and respect the show realize they did so more for the concept than the reality, while those who claim to distain the show overlook all the times they did get it right. Myself, I just did not want to have to fact check everything they were doing in every episode.
Take this particular video that we are commenting on. There are quite a few mistakes in Adam's understanding of the subtleties of what he is discussing, or maybe his understanding is OK but he is just erring in the way he describes what goes on. And things like "the 1st Law of Thermodynamics" is thrown out, when he was probably thinking "Newton's 3rd Law of Motion". But things like that add up, and can turn a good argument into a confusing one.
The test was done incorrectly
And yet still so many people just ignore the science for their own beliefs.
A convayor belt for a car would be a tredmill on the road. A convayor belt for an airplane would be a giant fan creating an equal and opposite tail wind.
I was met with this for the first time today, and I wanted to say it would lift off, but I couldn't justify my thinking, and I'm very thankful this existed to satisfy my curiosity.
They are incorrect because they focused on a different problem scenario.
The amount of frustration shown by Jamie throughout this myth and the length you went to test it made this one of my favorite episodes but least favorite myths
Yeah it was fun. Stupid but fun.
Yeah, its just too bad he was wrong. I love these guys, but I just looked up and watched the "experiment". The camera clearly shows that the plane is in fact moving forward. The myth is that the plain would not be moving (relative to the stuff around / background) due to the conveyor. If the plane doesn't move forward air won't go under the wings to create lift. Jamie said they tested this with an "ultralight". The tarp material probably didn't have much friction. That combined with the plane being light is probably why it was actually moving and not remaining stationary. If you put a heavy 747 or similar on an actual conveyor with a high friction belt, the plane would not be moving forward so there would be no air going under the wings to create lift.
@@Me__Myself__and__I OMG
@@Me__Myself__and__I
With properly oiled and working ball bearings within the tire mechanisms of an airplane, it is impossible for any airplane (no matter the size or weight) to not move forward through the air in relation to its surroundings.... assuming the propellers or jet engine is working properly. I’m pretty sure the question does NOT literally say that the plane is not moving in relation to its surroundings.
Also, the amount of friction between the tires and the ground is completely irrelevant if the tires are spinning freely and properly as they are designed to do, no matter what type of plane is used. It’s the same as a plane designed to float on water. No matter how heavy the plane is, and no matter what direction the water is moving beneath the plane, it will always take off because it is always pulled through the air by its propellers.
@@patrickb-man1309 That does not make any sense from a physics perspective. Imagine this, a fully loaded 747 sitting on a conveyor belt. Now start that belt moving and ramp it up to 100 mph (backwards). Does the 747 sit still in relation to the surrounding terrain? No, it ends up moving backwards at 100 mpg in relation tot he terrain. Now fire up the plane's engines to the amount that would normally cause 100 mph forward - and the plane ends up stationary in relation to the terrain.
It’s great how you’re not just jumping to the answer, you’re diving into what drives the debate; addressing the controversy, and how and why it keeps going, rather than just the physics question.
But the idea that THAT is the misconception is, in fact, THE misconception. Nobody (I hope) is comparing the plane to a car. We're comparing it to a passive cart pulled by a car. Putting a conveyor belt under the wheels of a plane is like putting a conveyor belt under the cart but not the car. If the surface of the conveyor always instantly matches the speed of the surface of the wheels, then the cart will never move unless the wheels slip.
@@bacicinvatteneaca In the cart analogy, just like the plane, if the conveyor always matches the speed of the wheel, then both will instantly approach infinity in the absence of friction.
If we had the alien technology to test this, the wheels and conveyor would instantly speed up to the point where the pulling energy of the car is cancelled out by the friction of the wheels.
The pulling energy has to go somewhere, you can't just store it in the void, and that energy is going to go to friction with an infinitely fast conveyor.
In the real world the conveyor/wheels would immediately melt and/or explode.
It's an underrated skill, yet not that hard to do. He's just taking his ego out and understanding the logic of each argument. Understanding the problem to find the solution without assuming your own correctness. I often see this with those math memes like 5/2(3+5). People choose the method they were taught as the only correct way to handle the implied multiplication with parentheses. The reality is both ways are right and have been valid in academia. No rule exists to address the specific issue because only an idiot would write it this way. I've explained the logic of both ways, including the mathematical principles that apply; and people still tell me I'm wrong.
This reminds me of the Veritasium video from a few years ago about a wind powered car that drove faster than the wind pushing it. I was working on my Aerospace Engineering undergrad at the time. The controversy across campus was so omnipresent that our final project for Advanced Aerodynamics was to write an entire engineering paper describing how we thought it worked. A full class of 25-30 aerospace engineering upperclassmen spent almost 4 months working on it with the most brilliant Aerodynamicist I have ever met, and we STILL couldn't come up with a confirmed, coherent answer because we didn't have enough data to explain it fully. Even through wind tunnel testing.
Engineering students aren’t real engineers, that’s why you never got an answer
@@Th3CrimsnChin What's a real Engineer?
@@Th3CrimsnChin This is like saying the person flying your plane isn't a pilot because they're a first officer, not a captain
Ive watched that veristasium video multiple times and still have trouble understanding
@Avendesora you mustn't be a captain.
Gear up, flap up, shut up.
"I'm just going to ignore that experiment" sounds really similar to "I reject your reality and substitute it with my own."
Wait, it’s only been 5 Mythbusterless years? It’s felt SO much longer to me! I thought at least a decade!
Ok
Same, it feels like it's been gone for much longer. I miss that show.
I also had to check wikipedia. I really thought it has been much longer.
what about mythbusters jr
I once landed with almost no groundspeed - very strong headwind, for a laugh my instructor got me to land in the width of the main runway at Filton (there's a small cross runway so it's all legal). Approach was like going down in a lift!
I wonder how you would flare the landing 🤔
I was heading down the comments to mention that lift is independent of ground speed - but Adam headed me off, anticipating the pedants, haha
So with that strong of a headwind, is landing into the wind pretty much your only option?
@@Matio25091 Depends how long the runway is. :-)
@@jimbass1664 Lol :P
I'm very greatful for Mythbusters as a way to settle such arguements! Though, as you've found, sometimes even seeing it doesn't persuade some people.
They are badly wrong in this instance.
If you really want to do a project properly to test these constraints, you would need one of two approaches.
First, install a measurement device on a wheeled vehicle to get the instantaneous rotational speed of the wheel. On the conveyor, you then need a controller that instantaneously matches the wheel speed.
The second option is to use two programmable motors - one on the vehicle wheels and the other on the conveyor drive. Set them to identical performance and then see what happens.
It should be self evident if they are set to the same speed.
Mythbusters did not ‘exactly match’ conveyor speed to wheel speed. They always fudged to reach their desired outcome.
Planes take off in relation to their airspeed. Take off distance won’t change at all, the conveyer belt just makes your wheels spin twice as fast.
I started off: ‘Well duh!’ And then changed my mind about four times before giving up and waiting for the answer.
That episode could also be titled "The everyday frustration of being an engineer reporting to non-engineers" 😁
Also "Why people avoid political discourse"
This came out when I was getting my Engineering degree in college and I was so annoyed trying to explain the propulsion of movement in an aircraft has nothing to do with the wheels. It was so painfully obvious.
"The everyday frustration of not defining your problems well enough"
I'm an engineer and pilot and my initial answer was no. When you say treadmill, I think something stationary but its wheels moving. IAS = 0 = no takeoff. And I think that's how they initially defined it. But then by the end the plane was moving forward relative to the air so of course it's going to take off, as the wheel speed doesn't matter. Depending on how you define the question, the answer can be yes or no.
@@chainringcalf what a relieve, I'm an actual aeronautical engineer and my initial gut feeling was "NO WAY THAT THING WOULD FLY" ( coz= no matter how fast the wheels are spinning, the wing is not moving relative to the air = no flights). The way you described it, stopped me from shredding my engineering degree :D
@@chainringcalf I like your version better, because you pointed to the core problem, compared to my rather superficial frustration of miscommunication.
It's often a mismatch between expectations and appropriately communicating them. I guess what makes things worse is, if someone is already settled on a design, vision or answer, and they refuse to leave their own shoes behind to understand the other side. Adam said it took him 10 minutes to explain this. That could also be translated to: "Take your time to understand, why another person says no or yes." And: "Take your time to not only tell your results, but how you got to them. Include your assumptions."
Came in with one thought and left with another thank you for teaching me something.
If the plane is moving forward, then the conveyor belt isn't matching its speed and you've done the experiment improperly.
"Go easy on people ... " FINE, Adam, FINE. I'll just delete everything I just wrote. It's FINE.
Idk man people are just stupid, I wouldnt hold back.
🤣👌
I can't 😂😂😂
Yeah its not about being dumb or not. Im a complete idiot and i got this one :D
It's fine, you are in the good place
i didnt quite unserstand the problem untill i heard: "cars mode of locomotion is it's tires contact with the ground"
and my opinion instantly switched. of course it's gonna take off
no it won't 😂
@@mikeuk666 Wait. Are you just trolling? I keep seeing you replying to every thread, spreading ass-backwards misinformation and replying to actual explanations with "No."
If you're not trolling, then please seek help. If you are trolling, please, get better at trolling.
@@foureye7058 You're feeding this deviant.
i remember seeing this episode and being dumbfounded that the pilot you hired thought the plane would not take off
Same here, and being just as dumbfounded now when I was reminded of that! A pilot really should understand the basics of how a plane works :)
Also, I find it funny that so many people are still arguing over this whole thing in the comments, while still not grasping even the most basics of basic physics. Perhaps its more sad than funny though, but as Adam said, people aren't (neccesarily) dumb for not understanding, but being dumb doesnt help :P
Yeah that is kinda terrifying to think about
@@Robinlarsson83 what part of "equal and opposite reactions" do people not get. blows me away too
@@HoldForHardFail yeah, I don't know :P a lot of people simply doesn't think very deeply (or even at all) on such things, it's sad really.
@@Robinlarsson83 You, and Adam, are misconstruing the question and are calling people stupid for actually engaging with it.
Saying "well the wheels dont generate power so they will be faster than the belt" is a lazy excuse for an answer, the spirit of the premise obviously means that the force created by the thrust is equalled out. so that v(plane)-v(belt)=0. If we accept this, the plane can't take off because there is no air flow lifting the wings.
The problem with the question is that thrust doesn't interact with a conveyor belt this way, and that for this premise to work, no matter the amount of thrust, the conveyor belt and the wheels would move at infinity and -infinty velocity repspectively.
So, the correct answer is not: "The plane takes off", the correct answer is "the premise is flawed and not worth engaging because it is impossible in a practical and really even theoretical sense".
You're being very generous. The real story behind this controversy is that ignorant people don't back down on the internet, even after reality has been explained to them ad nauseum.
Love how the controversy is about something completely unrelated to reality.
Have you seen what people cause controversies over these days? Nothing's changed.
there are people on this website that think planes are magic and don’t actually need fuel
@@DrRyan82994 What?
Hmm? But isn't EMALS still delayed? So as an alternative, refit aircraft carriers with long conveyor belts that move in the direction of takeoff. Landing could still get.. FUN!
i think the controversy exsists because some people are dumb and dumb people are really loud. those loud, dumb people are confusing leading to impressionable people being confused and sounding dumb.. so dumb people created the controversy creating more dumb people who create more controversy.......etc..etc it is a positive feedback loop of ultimate idiocracy
.
If I'm getting this right, all that happens is that the wheels rotate at twice the speed until the plane lifts off, due to the ground under them moving in the opposite direction.
And this brings up another point of semantics. What is meant by "the plane's speed"? Anyone reading the myth as meaning if the tires were connected to a speedometer will have a different thought path than some other statement of its speed.
@@globaldude100 Your first sentence is wrong: the wheels do not push the plane when it's on the ground either, it's still the propeller doing all the work. The only reason the wheels are there is to minimize the friction with the ground, but they do not provide **traction** (like they would in a car). If you look carefully at any landing gear you'll notice that there's nothing to make them spin. They're just like the wheels on a shopping cart (except for the turning around thing), they're free to spin forward/backward as much as they like.
A nice example somebody else made: imagine that you're standing on top of the a treadmill with roller skates on your feet, and you're holding on a rope attached to a wall in front of you. No matter how fast the treadmill spins, as long as you hold on to that rope you're going to stand still relative to the ground; and if you start pulling on that rope you're going to start moving forward! In this scenario, your pulling on the rope is the exact same force as the propeller pushing against the still air around the plane: it is not affected by the treadmill in any way, and it's the force that pushes you forward. The wheels on your roller skates are going to spin as much as they like, but they won't be able to stop you in any way.
To recap:
1) the propeller pushes against the still air, moving the plane forward
2) as the plane starts moving forward, its wheels start spinning as usual
3) as the plane is moving forward, the treadmill starts spinning in the opposite direction, making the wheels spin twice as fast
4) as the wheels spin faster, the friction with the ground increases a little bit, but it has an overall negligible effect on the plane's speed because the force of the propeller pushing forward is still much greater than the wheels' friction
5) the plane is able to pick up speed relative to the air just as usual, and will take off
@@MrShadowmaster00 I just phrased my comment poorly. :) I edited to make it better.
May not actually better.
Typed out alternate explanation in-between first comment and your reply. But didn't post cause we're all just trying to find different ways of saying: the wheels don't move the plane, the propeller does, and it pushes against the air, not the ground, so ground speed doesn't matter for takeoff.
In what I typed out, I also used the shopping cart example. :)
@@MrShadowmaster00 actually, I'm just gonna delete my comments since my bad explanation is just confusing. :)
The die hard "no take off" people say that the original wording was that the conveyor belt matches wheel speed resulting in infinite acceleration of the belt and enough force to stop the plane's engines from moving it forwards.
There's literally a small scale version of this at this science center in Orange County called the Cube. There's a model plane and model car on a circular track that you can spin up running opposite of both vehicles, and you have throttle controls over both vehicles. Sure enough, the model plane will always take off while the car can never overcome the reversing track.
That model is wrong. Planes get lift from wind not tires.
@@adetola1649which is exactly what the model is showing by the plane taking off but the car doesn’t go forward
@@adetola1649 Pretty sure the plane model works jus like normal plane with free-moving wheels.
you're right about the headwind thing, what's really the most critical thing to think about here is the vector equation at hand. In a textbook flight scenario, let's say we have a Cessna 172, typical high-wing, single engine monoplane, the engine alone doesn't have enough thrust stock from the power and propeller it has to lift the plane off the ground. Not unless it was a helicopter, which does work from that principle. The way a fixed-wing aircraft achieves flight, rather, is through use of the wings. The wings create an in-equal pressure zone over them as a result of the gases (air) at speed passing over and under them. The engine is simply there to propel or pull the plane through the air as they ride the wings. Simply put, in that scenario, unless you had something like a headwind or a giant fan to provide flow over the wings, the plane would not take off, and even if you did have said giant fan or headwind, it would need to be sustained until there would be a situation where you could get velocity over the wings of the plane's own accord, or enter "controlled flight" as the FAA calls it.
Hope this helps.
Miscommunication is way more common than malice. This is a perfect example of that.
But both Miscommunication and Malice have nothing on Semantics!
Except this isn't miscommunication, is misinterpretation of the problem.
When it leads to people choosing sides, jumping to conclusions, stating arguments and holding onto biases cause they feel attacked when you don't pick their side of the argument as the right one. This isn't miscommunication, its misrepresentation... the problem is no longer the plane on the runway, the problem is the scientific observers no longer being reliable.
The function collapses and scientific progress is no longer achievable, myths and fake news proliferates, human race dies a slow and agonising death arguing over semantics over global issues like climate change, viruses, pollution, vaccinations, clean energy.
@@mzaite Physics NEVER has semantics. There are people who understand it and there are people who have no concept of vector math.
@@dieselscience I've seen plenty of arguments about physics/engineering that hinge on differences in the meaning assumed behind a word or setup, between the opposing parties. (The plane on a treadmill, for one.)
@@FlyNAA In that case, at least one party involved in said argument(s) has no understanding of vector math.
....I remember that episode and I was highly disappointed that the pilot thought he wouldn’t take off...I was thinking “come on, man, if anyone knows how this works, it should be you”
That is incredibly disappointing.
That's because microlight operators aren't real pilots...like go-karters aren't real drivers :)
@@davedown-under6779 You telling me that a microlight pilot doesn't understand what makes his plane move and fly? You telling me a go-kart driver doesn't understand what makes his go-kart move?
Oh by the way...in reference to kart racers not being real drivers...Ayrton Senna would disagree
@@animalmother556x45 as would every F1 and 90% of closed wheel drivers (except rally they are an odd bunch) go karts are the starting grounds.
@@ccleadge Rally drivers starting grounds are 2004 Ford Focus on gravel roads haha (in the US anyway)
Safe to say, those people who didn't believe the outcome, rejected your reality and substituted their own.
One of my all time favorite phrases btw.
Reality wasn’t rejected, these clowns tested the wrong hypothesis.
@@zaddy83Found one lol
@@zaddy83 You clearly are a comedian.
@@ChristophBrinkmann how so?
The reason a lot of people are annoyed by his conclusion is that he did not properly test the question. The question said that the runway would match the speed of the wheels, not the aircraft. That means you can't just spin the wheels twice as fast, the runway will just move twice as fast which means all of the energy from the engines goes into spinning the wheels faster and faster forever until the plane runs out of fuel. Obviously doing that in the real world would be impossible but Adam is trying to say that he has the only right answer and anyone who disagrees based on the content of the question is wrong.
I work at a small airport and when high winds are expected the planes are hangared for the most part. The ones that cannot be hangared are faced into the wind and tied down securely. Even then, they will bob around and the wheels will lift off the ground once in awhile from the wind. If they are faced in another direction they will break the ties and flip over.
Would be a fun (but dangerously stupid) attraction to tie an airplane to a pole or rope in a storm and then fly it in place
I had not seen this riddle until recently, and saw it twice in short amount of time. I actually used that as an example, along with a kite. In theory, a plane sitting still, with just a high enough head windspeed, could lift off a plane, without the plane moving at all, including a 747 jet. Would take an extremely high amount of windspeed to do it, but in theory, it could.
Remember my first episode of MB that I watched with my father, now long gone, sadly. It was burn the enemy ship down with mirrors. He watched and then gradually begun to turn red in the face. Then true to his enginnering heart, he finally lost it, shouted to the TV: "The tolerances, the tolerances, you can burn it down in minutes. Just fix the tolerances! Bums." :-) That is a dear part of MB I will never forget. Thankyou for the memories, Adam.
Edit: engineering
"fix the tolerances!" is exactly what I thought at the time (and still think). Shame on your father for ignoring how devilishly hard it is to fix those tolerances; as an engineer, he should know better.
@@RonJohn63 pretty much. If they couldn’t, neither could Romans.
@@extrahourinthepit Why not? The Greeks and romans were able to build sophisticated machines, they could make smooth mirrors and probably measure angles precisely. The problem would be having everyone track a moving target. If every soldier were trained on how to position their mirror accurately using muscle memory it might be possible, just like how a well trained archer can exactly position their arms to hit a target hundreds of meters away.
@@takanara7 but still nowhere near today. Again, if someone with modern day ways and means could not, neither could Romans.
@@RonJohn63 Shame on who?
The plane does not have “drive wheels” - they spin freely. Assume the required take off speed is 30mph and the belt is moving 30mph in the opposite direction. The plane STILL moves forward at 30mph like normal, but the free wheels are spinning at 60mph.
They perhaps should though, because of the immense amount of fuel relative to amount of movement required for taxiing.
But what if the belt speeds up to 60mph when the wheel tries to spin that fast?
@@punkdigerati You would then need to have wheels that somehow automatically clutch/de-clutch themselves so that landing is possible, otherwise having wheels that don't match the relative ground speed exactly at the point of incident would result in many exploded tires... And by extension, planes.
Or separate sets of retractable wheels, one for taxiing and one for landing/takeoff, but that sounds like both a weight and engineering nightmare.
@@hyphz Then the wheels will speed up to 120mph and the plane will still be moving forward at 30mph like normal. Less a tiny bit due to drag, but not enough to noticeably impact the take-off speed. As per the test Adam described.
@@Temp0raryName And then the belt speeds up to 120mph.. and so on until the belt or wheel reaches the physical limit on its speed. Presumably then the wheel would strip its treads and skid along the belt. But it's a shame this wasn't addressed.
Dang, for like the first four minutes I thought I was one of the people who understood it perfectly… then you mentioned cars and I went, “I’m an idiot.”
You're not an idiot, Adam is WRONG. czcams.com/video/Y64ZdSaDdoo/video.html
It is quite simple when you understand it. But there are teo versions of the problem
This is a wonderful problem for college level physics (or better high school than what I had!) to understand different reference systems regarding measurements.
For takeoff, the critical parameter is wind speed. Once you achieve takeoff windspeed the plane flies.
Now you have ground speed - how much the plane moves regarding something static - say a post on the ground. You normally achieve takeoff if you achieve a given ground speed - as long as the wind doesn't mess you up.
And finally, conveyor speed which is almost trivial once the plane starts its motor system it'll push against air and will essentially ignore it.
I know many of my fellow engineering students (both colleagues and later as a TA) would have been tripped over this, and then eventually understood how the systems works. I love this episode - I got it "wrong" but realized the problem once the plane is actually "moving" against the air and ground, not the tarp. It really is a matter of defining the right system.
I think "language can be confusing" is one of the larger root causes of people misunderstanding science and experiments like this in general. Which to me just reinforces the importance of education.
Live these little videos. Thank you.
I love this explination and I myself had an "oh, right!" moment when Adam unraveled the explanation. I also loved the emotional inteligence Adam displayed in "being easy on ppl and understanding our own biases."
Yep, at the beginning, I was like, no way It'd take off, but once you grasp the understanding it's a very "oooooh" moment.
I had the same initial impression that it shouldn't work at the start, but then thought of it from the angle not of an aircraft taxiing to its starting point on the runway, but as it would use its props/turbines to propel itself, thus creating the necessary wind (by moving itself through the air, rather than the air moving from point a to b) to achieve lift.
Same experience-but when Adam explained it I was like, “oh right that makes sense now.” Adam is very kind to say that people aren’t being dumb. People should be able to change their minds when presented with evidence.
@@maniac7770 When taxiing the vast majority of airplanes also use props/turbines to move. Some in-wheel systems exist for some commercial aircraft but I don't think they're used much.
"i cant help people like that"... those are the physics versions of flat earthers
There is an opposing force. The wheels have friction with the ground. This friction depends on the weight of the plane. So as the plane speed increases , the wheel speed increases , the conveyor speed matches that and the airplane remains stationary relative to the air and ground. It cannot take off.
Aircraft have an order of magnitude more thrust than any wheel drag can ever amount to.
You are essentially saying a conveyer belt acting on freely spinning wheels, which are supported by bearings, can somehow overpower a freaking jet engine?
As a mechanical engineer, I acknowledge I had an edge in answering this correctly (I did not see your episode prior to seeing this video, which is weird because I've seen so many MythBusters). But I immediately answered and answered "correctly".
That said, there is a force you did not mention: The friction of the wheel bearings. Since the wheels are experiencing double the speed the plane is going (in the ultralight example it's 25mph forward through the air but the ground is moving at -25mph so you get 50mph relative movement between the ground and the wheels), a plane with a takeoff speed of 100mph would have the wheels experiencing 200mph. And that friction works against the thrust generated, meaning you will need more thrust to go the same speed. At 50mph the frictional force is likely minimal but at 200mph or more, it could get more significant. I'd be curious to know how this would affect a much larger plane with higher takeoff speeds.
I remember when the penny dropped for me and I suddenly understood this problem. When you grasp the fact the plane's wheels aren't powered and they'll simply spin faster to overcome the moving runway, it feels just as obvious as thinking the plane won't take off. And I've flown planes and I know enough of the physics and it still took me longer than it should have ...
100% this!
Adam and so many people miss a very important text in the problem: “the conveyor belt is designed to exactly match the speed of the wheels”. This necessitates that the wheels can’t “simply spin faster” to overcome the moving runway
@@dadabeaux_productions That is incorrect. The treadmill could match the speed of the wheels at all times. If the wheels start moving faster, we increase the speed of the conveyor. Even if you do this perfectly, it will not prevent the plane from moving forward. It will still take off. Your misconception is that the speed of the wheels matters at all. It doesn't. The treadmill could be moving at 5000mph and the plane would still move forward and take off. If you disagree, explain how you would change the experiment.
@@meepk633 I'm more confused on the air speed part. Yes the propeller will be up to speed and what not but isn't that like holding the ass end of a rear wheel drive car in the air, full build of revs and then dropping the car to go? The car will not go 180mph right off the bat there will be a build up. I'd like to see what the air speed and ground speed says when on said conveyor belt and throttled to take off. I think using an ultra light was a huge mistake in this myth as ultra lights can take off stationary with a strong breeze. Let alone once they are in the air the power to weight ratio of an ultra light is ridiculous. It will easily get to 25mph from stationary in the air. I totally see it working with an ultra light but I'd like to see how it plays out with a plane with a not so high power to weight ratio.
@@samwisegamgee3596 The plane only needs a PWR high enough to overcome the friction in the wheel bearing. An ultralight and a fully loaded 747 can both overcome that friction at idle. It doesn't matter how fast the treadmill is moving because the two components of wheel speed are additive and unrelated: speed of treadmill + speed created by propellor. You can change one or the other independently.
Someone else in these replies stated it way better. Imagine you put a skateboard on a treadmill. Sit on the skateboard while facing backwards. Now hold onto the stationary sides of the treadmill. What happens when you turn it on? As long as you're holding onto the treadmill, you stay in the same place. The wheels spin freely under you. In order to move forward (or backward), all you have to is impart a small force with your arms. There's no way to change the experiment--no clever acceleration curve of the treadmill--that could prevent you from moving forward or backward freely. Like the plane, the wheel speed is unrelated to your motion.
I feel like this is more of a riddle than a controversy because once it’s explained to you it makes a lot of sense
Well that's a lot of the myths on the show
Physics, it's just crappy riddles.
People who make real riddles would be offended by this. There’s nothing clever or devilish about the question, and Adam going out of his way to defend the people who don’t get it is asinine
You would think that, but there are a lot of people who just seem to be unable to grasp the concept of how a plane moves VS how a car moves. I remember using a very similar explanation that Adam said, and tons of people then trying to tell me how I was wrong.
Sorry to Adam but Propeller or not, there's still no airspeed on the wings to create lift on the wings, so therefore the tires are still touching the speed-matching conveyor holding it stationary (0mph) and the conveyor will still be the dominant force along with gravity cause nothing is now fighting against gravity.
Ok, there are 3 speeds that’s the easiest way to understand this.
1. Ground speed (how fast the plane is moving in relation to the ground)
2. Wheel speed (how fast the wheels are spinning, each wheel can rotate at different speeds due to size and a number of other things)
3. Air speed (this is the only one that matters to a plane)
A nice way to test this at home/for cheap easily is to take a threadmill, a peice of string and a hotwheel. First attach the string to the hotwheel and pull it across the threadmill while it’s off (try to get a feel for how much force it took to over come the rolling friction and pull it across). Now turn the threadmill on at any speed setting you want the amount of force/tension in the string to roll the hotwheel across will always be the same no matter the speed of the threadmill
"because I disagree with the outcome, I am going to ignore any empirical evidence that says I'm wrong" is one of my biggest pet peeves! The fact that such a mentality never appeared in Mythbusters was also one of the things I appreciated and respected most about the show. It was the best example I've ever seen of refusing confirmation bias and searching for genuine answers. I honestly believe I wouldn't be half as well educated as I am without Mythbusters setting that example of genuine curiosity unconcerned about who's right or what conventional wisdom has to say on a subject. Thank you for that Adam! you and Jamie and the whole rest of the crew have tangibly changed my life for the better in that way.
And one of mine is people misrepresenting things as just rejecting empirical evidence, as that is another form of confirmation bias.
You think you have results that support your position so you dismiss anyone objecting to it in any way as confirmation bias.
They aren't simply rejecting it. They are saying it doesn't match they conditions required. They are saying the experiment doesn't fulfil the required conditions and thus does not support the claim.
@@jeffreyblack666 I agree. That is an equally big problem, and one which I'll admit I'm sometimes guilty of, but I'm trying to be better. I think Adam made a really good point in this video about trying to understand the semantics of both sides of the argument. Because if people can suspend their expectations and take the time to listen to every side of an argument and their evidence, and then work together to figure out where any communication is breaking down, then both our pet peeves could be avoided.
@@DaveTpletsch And my point was that Adam hasn't fully understood the semantics of the other side.
But yes, I agree that actually understanding what the other side is saying, rather than making assumptions about them, and importantly, distinguishing between reject results vs rejecting what those results mean, is key to further understanding and getting along.
I am that person, in the 15 minutes I've known about this topic, although I will say my misunderstanding ultimately comes from the fact that I've never studied aerodynamics (but am an engineer). Regardless I agree with Jeffrey, because I get what Adam is saying, and yes he tested it, but I'm still stuck on the semantics of the question, and I think it's ultimately the point of reference that is at question.
Those that disagree with the experiment, for me at least, expect the plane to remain stationary, and in the experiment, it did not. Which throws out the whole experiment, because even as Adam mentioned, it should not take off, if the plane is stationary. So it is not a rejection of the experiment, but a questioning of the parameters in the experiment. But I understand his point, and plan on looking further.
@@Jarrettmonty99 The whole point is that the plane doesn't remain stationary on a moving conveyor belt; if the conveyor belt had moved 3 times at fast the plane would still move forward, the wheels just spin faster.
This is one of those questions that is specifically designed to trick people into saying the wrong answer. People don't say the wrong answer because their understanding of the physics of the question is wrong, they say the wrong answer because the question was worded in such a way to draw them to the wrong conclusion before they take into consideration the factors which would lead to the correct conclusion. The second somebody said, "Now try to build it and see what happens," you'd immediately realize why your answer was wrong. And you'd feel like the question tricked you, you wouldn't feel like you were too dumb to understand the physics.
Anybody who says the plane wouldn't take off if it had no motion relative to the earth (and by extension no motion relative to the air) would be correct, physically speaking. They just made an assumption that the whole point of even mentioning the existence of a treadmill is because it would result in this zero relative motion. That assumption was incorrect, but they only made the assumption because why else would you ask the question unless that was supposed to happen?
I agree. This is why the people on the forums Adam mentioned argued the experiment was wrong.
(On top of the standard internet cannot-be-wrong).
The experiment the Mythbusters conducted genuinely wasn't the way they interpreted the question.
This is the physics version of 5 + 6 * 4 = ?
@@xdevantx5870 Well, that question is just basic order of operations. A lot of people who get it wrong actually just don't know how to do math, and anyone who knows how to do math won't get it wrong because there's nothing to actually be confused about. Sometimes there are questions around order of operations which are intentionally a bit ambiguous (often using the ÷ symbol, which isn't really used by real mathematicians.) Got example, 6 ÷ 2(1+2) = ? For this question my personal answer would be 1. This equation is vague and has no well defined answer. In my opinion, the 2 before the parentheses is acting as a coefficient to the value within the parentheses, and so that whole quantity should be calculated before the division happens, i.e. 6 ÷ (2(1+2)), resulting in an answer of 1. Other people might say that the equation can be rewritten as 6 ÷ 2 × (1+2), and then it would be calculated to equal 9. Depending on the interpretation of the question, either answer can be right. But the point is that the question just shouldn't be written the way it was written, because it's ambiguous.
I'd say a more comparable case of trickery is when somebody tells you to say 'milk' 10 times and then quickly asks you what a cow drinks. And the answer is water, but they already put the idea of milk in your head, and your gut reaction when you think of drinking and cows together is milk.
@@MattMcConaha Order of operations are just conventions. The math question is written misleadingly. Just like you can get to the right conclusion about the Plane Conveyor by understanding the problem, but it's written misleadingly.
What I see as the major source of confusion in this question is, I often see it worded as "the tread mill exactly matches the speed of the tires." Taking out of account whether the plane could use thrust to move forward (it could and would eventually take off), the wording means that no forward movement and therefore no airspeed is gained. If the treadmill is exactly matching the speed of the tires, no matter what that speed is, the aircraft is not moving forward and therefore not taking off. This comes down to tricky wording.
There are two ways to phrase this:
1) The treadmill matches the speed of the wheels spinning.
2) The treadmill matches the maximum speed of the plane.
They did option two here, with an obvious answer, the wheels just spin twice as fast.
But with option one it is basically impossible, as once the plane starts moving the treadmill would have to accelerate indefinitely spinning the wheels faster and faster but failing to slow down the plane. So either the treadmill would fail to keep up, or it would move fast enough that something broke, maybe the wheels melting?
There are a nice round 13,200 comments prior to mine, and I admit to sampling only a portion of them. Adam, your explanation is, of course, spot on. An easy way to help the explanation:
If you had a speedometer attached to the wheels of the airplane, it would show 0 mph/kph/kts at rest. As the conveyor belt started to move the plane, if tethered to a pole, would show a speed equivalent to the conveyor belt speed. The airspeed indicator would show 0.
Cut the tether, and let the propellor go and now the airspeed indicator will come alive and the airplane will move forward. The wheels will continue to show that speed and it will increase such that the groundspeed shown by that speedometer will be the sum of the two speeds -- conveyor belt and airspeed. At some point the airspeed will reach the V2 speed, at which it can take off even with engine failure. At that point the speedometer will show the sum of both that V2 and the conveyor belt speed.
To make this even more understandable... pretend that halfway through the airplane accelerating from 0 to V1 the conveyor belt is turned backward, so that it's now pulling the ground out from underneath the aircraft. Other than reducing friction on the wheel rotation, the only difference is that the speedometer will get around to showing a speed lower than the airspeed.
None of the speedometer displays or the wheel rotation rates matter at all. What matters is airspeed. When the airspeed reaches V1 the airplane takes off regardless of whether the wheels are spinning super-fast clockwise, counter-clockwise, or are stationary.
Ehud
Tucson
Arizona
Certificated FAA Commercial Helicopter Pilot. Runways are for models.
Good thing you aren't a airplane pilot. We get airborne at Vr not V2. V2 is one- engine failed safety speed for second segment of an engine failure climb profile. Must be reached by 35 feet and still the airplane must be accelerating to Vyse
An interesting way to conceptualize it is that the conveyor belt is effectively acting as a frictionless plane; the car can't move because the tires can't push against anything, whereas the airplane can just slide across the ground with no issues.
I like this. Made the think of this analogy. If you put a car out on a frozen lake that's completely smooth and a little wet, no matter how you mash the accelerator, the car can't get friction and won't move. A plane set down right beside it, when the throttle is pushed forward, will glide across the ice and take off.
But it's wrong. Friction is transmitted through the wheels, the plane doesn't slide, it just "mostly" slides. A fast enough conveyor could push it back.
@@SgtLion it would probably also break off the wheels at that speed, but the premise is that the conveyor is moving backwards at the same speed as the plane is trying to move forwards; the wheels would be turning at twice the speed they normally would for takeoff, and the additional slowing power that the friction would provide would be negligible
@@SgtLion You're going to have to explain this concept of friction being transmitted through the wheels. That doesn't line up with any of the physics classes I had. As the wheels spin faster and faster they would heat up due to friction, but on a frictionless surface, the wheels of the plane would never turn at all. They would remain completely stationary as the plane accelerated forward. You have to have friction in order to make the wheels turn. On a frictionless surface, you could replace the wheels with skis and achieve the same result. You put skis on a normal runway and they would shear off due to the friction.
@@garryuyahoo And there are plenty of planes which use skis and pontoons and so on, instead of wheels, too.
Me at beginnings: of course it won't take off
Me at end: ahh yes, propeller goes brrrrr
When I first watched the episode I thought they were going to hold the plane in place and move the runway beneath it, and of course that wouldn’t work so I was confused why it was even being tested
Underrated comment
You sir have earned a chuckle out of me.
A buddy of mine asked me this a few years ago and for a decent bit we went back and forth on it. I think it was the first time I really stepped back from something and decided I wanted to learn and be better instead of be obstinate and be 'right' in my mind. My closing argument was that we were both right because there is a chance the tires would be spinning too fast and they could delaminate causing damage to the plane 🤣
At that point, you would be running up against the tensile strength of the runway material.
You couldnt have explained it any better with this controversial topic , i literally watched so many videos trying to confirm my hypothesis why it would takeoff .Thanks alot for this explanation
Unfortunately it is wrong ... but depending on the way the question is stated.
"Thousands and thousands of websites devoted to people arguing"
Yeah that sounds like the 2000s
And now it's consolidated into the cesspool that is Twit-ter...
@@shinigamimiroku3723 as much as I despise social media, I suppose I should give it some credit for largely consolidating this crap into areas I can easily avoid. Still a blight on society though.
The question isn't complicated. People are stupid. A treadmill works on people because people use the ground to propel itself. But a plane doesn't - a plane uses the air to propel itself.
Meanwhile in the youtube comments section...
Now social media tells us what opinions to have.
the thought Steve-O from Jackass was part of this show made me smile for a second.
"Hi, I'm Steve-O and this is Plane On A Conveyor Belt!"
I totally understand the physics, but I thought the plane wouldn't take off because I didn't fully understand the function of propellers. I thought the wheels were the primary driver to get a plane up to initial takeoff speed. I knew that the propellers functioned to pull the plane forward as described here, which would obviously HELP on the ground, but thought their primary function occurred AFTER it was in the air, when ground friction was removed. Once I learned that propellers are so pivotal (no pun intended! :D) on the ground, the rest of the explanation makes total sense.
I mean, the friction from the ground via the wheels is probably almost negible on take off, wheels and ball bearings are very effiecent :) The main force to overcome is the inertia of the plane it self.
@@Robinlarsson83 how does it take off if there is no air moving past the wings? or maybe i dont get propellers either, but if the wheels are allowed to spin into infinitum you never get any air moving over the wings aside from just natural wind maybe
This is my first time hearing of this controversy and it took me all of 10 seconds to deduce that the plane would in fact take off... the planes forward thrust is being applied to the air. The backwards moving runway might slow it down a TINY amount because of rolling friction in the wheels, but overall it would do almost nothing to prevent it from taking off. It's pretty disappointing knowing that so many people had it wrong.
“We are tied down to a language which makes up in obscurity what it lacks in style.” - The Player, _Rosencrans and Guildenstern Are Dead_
Anyone who quotes that film gets a like from me.
@@discipleofthecapedbaldy962 “We are tied down to a language which makes up in obscurity what it lacks in style.” - The Player, Rosencrans and Guildenstern Are Dead
We don't even listen to the language. The plane won't take off if it doesn't move forward. If it doesn't move forward the speed the conveyor belt has to match is 0mph. The plane moving forward on the conveyor is a prerequisite for the myth to exist. Game, set and match. 😎
It was a very good play and movie
@@AnttiBrax Yes, that's once You've realized, that the plane creates thrust by pushing against the air.
If You go to the root of the confusion, assuming the forward motion coming from wheels turning against the ground, then the conveyor would have to counter the rotation of the wheels to actually keep the plane from moving.
Adam: "I reject your reality and substitute my own"
Also Adam: "I can't help people like that."
:) I get it, though. Thanks for this video!
Need to interject here. While the experiment showed that the plane would take off, the experiment itself was fundamentally flawed, and I'll explain why in a few lines. This is not a dig at Adam whatsoever. But in order to answer the question portrayed, the details have to be absolute. No new variables or flawed math, intentional or not.
The wheels and the conveyer belt are the ONLY variables that matter and I'll explain why in a few lines. It's a fundamental physics problem. It does not matter if the wheels and engines are mechanically connected or not. Adam is a great educator, actor, tv host, etc., but he is not a scientist or engineer. It's not a problem of if the plane can reach a speed to take off. Obviously a plane needs ample amount of lift to take off .It's a problem of if the plane will move whatsoever. And the physics of the problem stated does not allow the plane to move.
This is COMPLETELY wrong, and I wish he would just go do more research instead of sticking with his guns in the "my experiment proved it so it cant be wrong." fashion. I grew up watching Myth Busters and absolutely love the show, but experiments do not always provide correct outcome if the variables are not perfect and if external variables are added.
The mode of force, tires vs propeller/engine are irrelevant. The ONLY variables that matter are the wheels and the conveyer belt. It doesn't matter if its a propeller pulling, an engine pushing, the wheels mechanically turning, a person off the conveyer belt pulling, any of that. If you tied an infinitely strong rope to the front of the infinitely strong hull of the airplane and applied an infinite amount of force, you would not be able to move the plane. The only thing that would happen is the wheels and conveyer belt would reach an infinite speed.
This concept is so hard to grasp because it's out of touch with reality. 99% of physics questions taught in classrooms happen in a perfect hypothetical world, and could not exist in the normal world. And if they did, the results would be drastically different. This is one of those questions. There are two main reasons that the experiment that you did were flawed.
1a. It is impossible to instantaneously match the speed of the tarp and the speed of the wheels on the plane.
1b. As the plane tries to take off, the acceleration of the truck needed to accelerate match the planes speed. Going the same speed as the plane is useless. The math does not add up.
2. The tarp that you pulled was also in contact with the ground and not supporting the weight of the plane. Thus, the plane was able to use the ground underneath to help propel itself forward.
It's even impossible to replicate the perfect experiment no matter how much money you throw at the project. So you have to rely on fundamental physics to figure out the problem.
Breaking it down fundamentally.
If the circumference of your tire is 1 meter, as the tire rotates, the conveyer belt moves back 1 meter, matching the speed of the plane's tires instantaneously. In order for the plane to move horizontally, the tires have to rotate. And the tires cannot rotate without the conveyer belt moving the opposite direction the same distance at the same speed.
I've never heard this question and was thinking through it as you were explaining, ultimately coming to the incorrect conclusion before you explained it. The funny thing is, I even told myself I was wrong, amd still got it wrong. I thought "ground speed is irrelevant to an airplane" but still couldn't make my brain realize that the treadmill wouldn't pull the plane back and cancel the airspeed, at least not to a significant degree given normal drag and friction. Very well explained sir.
Most people who haven't flown a plane or played with flight simulator or been big aviation fans don't think about how plane wheels are literally free-spinning: they have brakes but no propulsion and are rated to operate reliably in extreme environments. It's counterintuitive even for pilots: strict procedures have to be enforced for chalking (immobilizing) plane wheels when parked, tying smaller planes down to cleats sunken into the concrete parking areas when unattended, and specific operational procedures with the engine and landing gear to avoid common "gut instinct" mistakes. We're used to walking and driving, the idea of moving ourselves across the ground using a big fan is not intuitive at all.
Boat operators get into similar trouble: depending on how your propulsion works, you may lose steering or braking ability when the engine is low or off, and momentum across the hull in the water versus whatever conditions the water may be in can change performance radically. It's just not intuitive at all.
As just one example, many commercial planes have enough engine braking (reverse thrust) ability to back themselves away from a terminal, but they're prohibited from it because that would kick rocks and dust up onto the terminal windows, not to mention be a poorly controlled maneuver in a tight chaotic area and planes dont usually have rear view mirrors. So a little truck pushes the planes back and safely out of the way instead. What a plane can do and what we want it to do are only sometimes in alignment.
@@WBWBWBB doesnt the plane need air moving over the wings to lift of though?
@@Healcraft yes and a plane on a conveyor belt does get air moving over the wings, because its engine pulls it through the air, because the conveyor belt doesn't affect the ability of the engines to pull it through the air, because aircraft wheels are like roller skates: they could spin a thousand miles an hour and it wouldn't be enough to prevent the engines from pulling against the air and driving the plane down the runway. The most you'd get is a slight backwards motion before the engines fully engaged. It's a misleading word problem like "how will a car drive forward if it's in a wind tunnel that matches its speed but in reverse" except since people are more familiar with cars than airplanes people actually get stuck on it. We know cars can move in heavy wind because their motion is tied to wheels on the ground. Likewise planes can move on fast ground because their motion is tied to engines in the air. (That's why seaplanes work: wheels are nice for the ground but they're not necessary for flight.)
@@WBWBWBB Thanks for the writeup but since I wrote my comment I was thinking on it and kind of "got it" eventually. I think the wording throws me off because , to use your wind tunnel car example, my brain interprets it as, how can a car drive forward if you put enough wind to stop it in a wind tunnel, im sure there is a strong enough wind that can stop a car in a wind tunnel, no? So to do the experiment on the plane correctly, it (the converyer belt) would have to be going insanely fast and then the wheels would just pop off anyway I think. But with infinite no friction wheels that cant break then it just takes off as normal.
@@Healcraft exactly, the wording of "matches the speed" or whatever implies some kind of relationship that not only totally changes the experiment but almost invalidates it because it's getting into extreme physics instead of the apparent basis of the question. And I'm actually not sure if there's any amount of wind that would prevent a car from moving forward unless that wind was also lifting the car up or destroying it. The engine will turn and the wheels will turn and the rubber will rotate against the pavement and unless the car is really un-aerodynamic you're talking about hundreds of miles an hour of wind versus 0.01mph car still moving forward. As you said, you're quickly talking about catastrophic conditions and not any kind of "and then the plane stood still" sort of effect. Yes, if you somehow manage to grab a hold of the plane's wheels (or skis, or skids, or undercarriage) and hold it in place, its engines will struggle and the plane won't take off. But that's not the question, the question is "a treadmill," which we're supposed to understand is operating essentially like a car on a treadmill (which would stay in place just like a car on a dyno.) And so the plane would take off, because planes don't give a crap how fast their wheels spin up until catastrophic damage.
This discussion just came up in my friend group and we talked lengthy about it. We came to the final conclusion that the plane wouldn't take off for the following reason: The scenario is explicity "the conveyor belt matches the speed of the wheels", so when the plane accelerates into one direction the conveyor belt does so in the opposite direction, increasing above the 25mph takeoff speed. Because of this the friction increases and the plane experiences drag from the ground/wheels matching the propulsion force of the propeller. This or the relative speed of the wheels to the conveyor belt would exceed the wheels or conveyor belts limits and they'd explode.
watch it again. lol you are still hung up on the wheels, it could have wooden skis on it and it would still take off
To add something:
Some people believe that a plane is driven by tire until its speed is fast enough for the air to create lift.
Yeah for some reason I was thinking that while watching this but I also wasn't thinking of a propeller plane (even though a commercial plane would also take off)
@@Uncle_Yam what kind of plane were you thinking of then?
I literally thought that so yeah lol
Is there any plane in existence that has motorized landing gear? I assume that there must be one in existence that is the exception to the rule.
@@ashakydd1 There's a system called EGTS under development, but it has nothing to do with takeoffs and landings. It uses electric motors in the wheel hubs to save energy during taxiing.
When I watched the original show, I was certain that the producers had told the pilot to insist that he could not take off from a "runway" moving in the opposite direction. Here, Adam is reporting that the pilot was genuinely surprised by the result.
As humans can't fly, we can't move ourselves without needing the ground, so if the ground moves the opposite way to the way we try to move, we get there slower or not at all. I imagine this is why we will think about the ground moving 'backwards' like this, at least at first, even if things we use operate differently. 'If I'm on this runway, can I get to the other end? No, therefore a plane can't take off if it's not moving towards the other end of the runway either'. But the plane *is* moving towards the other end of the runway because it's not dependent on drive off the ground, unlike a human.
If you could ask the question to a seagull then I think they'd get it easier than a human, although now I want to see a seagull taking off from a moving treadmill, because I don't know if they actually need a little run up to get airborne. They would at least intuitively understand how they could take off without them or the ground moving forwards when the air speed is high enough for them to glide on the spot, or without moving forward relative to what they're standing on, like a car. They can just spread their wings and lift off of it.
He probably shouldn't be a pilot if he doesn't know how planes work on a fundamental level
I just cannot honestly believe that a PILOT would not know how a plane works at such a basic level. The question is so obvious if you know that plane wheels are not powered so it doesn't matter what the ground speed is, only the airspeed.
Really disappointed that he still didn’t address the actual question. The treadmill isn’t matching the PLANE’S speed backwards, it’s matching the wheel (the rubber).
The reason it’s a great crazy question is that the pushing air propulsion vs friction with the ground propulsion actually has nothing to do with the answer!!
This is one that mythbusters got it wrong.
You explained it so well!
I think the controversy was because lots of people thought the question was: Will the plane with zero airspeed vertically take off because of the motion of the treadmill? I remember lots of the NO crowd was mad because they thought the yes crowd was arguing that point. Seems to me this thing was mostly two correct groups answering a different question.
Exactly and I feel like whoever first asked the question intended it to be that zero airspeed interpretation. The question that was answered was more like: What happens when a plane tries to take off from a conveyor belt that is moving faster than the plane's takeoff speed?
It’s weird to me that someone would even assume that that’s the question being asked cause that’s a dumb question to ask. No one would even expect the plane to takeoff when stationary in the first place.
I thought the correct answer was so obvious that the only way I could explain the "no it wont work" crowd was if they were answering a different question. MB crew should have recognized that and specified which question they were asking.
@@justin66asdf Yeah they never really approached the question, but complaining about stuff like that was part of why we watched MB
What? I was hugely involved in the debates back then, and I never heard this even once
The human mind, once sufficiently invested in an idea, finds it very hard to let go.
No. It's actually the opposite. Confirmation bias kicks in quite quickly. We adhere to our snap judgments, and only when we work to investigate why the opposite of what we believe might be true can we hope to undo those snap judgments.
That's not the opposite, that's what they were saying.
@@Mirality It kind of is, because there's practically no "investment" in the idea. It's one thing to believe and develop an Idea like the Geocentric universe then have trouble accepting the Heliocentric reality.
It's another thing entirely to latch on to a whim you've given zero thought to and defend it with a furor equal only to the pigheadedness of a god.
@@mzaite Except that is exactly what happens. The OP quote might be better stated "The human mind, once settled on an idea, finds it very hard to let go". It may take very little mental effort to initially settle on an idea initially, especially if it superficially "makes sense". That is the trap of the mind. Ideas are easy to adopt as long as they don't directly contradict other ideas we already hold, yet are devilishly difficult to be rid of once they are adopted.
Arthur Schopenhauer, “All truth passes through three stages: First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as self-evident.”
I know I’m late on this one, but…. I wanted to also add that cars transfer mechanical energy to their wheels in order to move. But to my knowledge, small general aviation aircraft do not.
I can't believe there is any kind of actual controversy whether or not a vehicle that's not motivated by ground contact can take off into the air. Guess this is why most folks aren't engineers.
Episodes like that is what made mythbusters so damn good to watch..
Yes, and I miss Mythbusters a lot. It is my all-time favorite show. I loved that I was a participant in the show and not a passive viewer, in the sense that I was trying to solve the problem while watching.
Also, Kari Byron didn't hurt its watchability any...
@@KnuckleHunkybuck Are you kidding? She WAS the reason I watched :)
The best way I had this explained was from my dad(a licensed single engine pilot and engineer) a car pushes from the bottom, a plane pulls from the top. It doesn’t matter if the conveyor moves at 100 and the plane takes off at 70 the plane will take off. He said that the moment he heard the myth on that episode. Always stuck with me
Yeah, but what if you are standing on the breaks !
Yuppers. The only bottleneck is rolling resistance. If you have some combination of unusually high rolling resistance in the wheels and the runway whipping backwards fast enough, you might produce enough effective drag by way of the landing gear to delay takeoff by a few seconds. Crank the rolling resistance up real good by feathering the brakes or something, and that may in fact manage to counteract the thrust to the point that you can't quite make takeoff speed. Granted, that works pretty well on a stationary runway too. It's also great for making your wheels catch fire as the brakes are converting your engine thrust to rather localized heat, so maybe don't?
@@Archgeek0 even if it was possible to make a conveyor belt that goes at a sufficient speed to cause enough drag from the tyres and wheel bearings.......that pull is only going to be relatively minor. Especially if it was possible to make that conveyor belt, it would also be possible to fit a plane with a sufficiently strong engine to power it with the brakes on, it would still be able to take off (albeit in a huge cloud of smoke, with the landing gear being so trashed you probably couldn't land it!)
And unfortunately, he was wrong. He didn't think about the conditions of the problem. The plane is required to be physically restrained from moving forward. It cannot take off.
@@RockinRobbins13 Uh, not quite, at least not in practice. There is no restraint to the plane, just the swiftly moving tarmac belt thing. Without much rolling resistance to back that up, the wheels' bearings make it all for naught and the plane gleefully pulls itself through the air until it's got the needed lift. Only terrible wheels with a lot of rolling resistance can provide any real opposition to the props' thrust, so you generally get a take-off regardless, unless you do something dopey like press the brakes to artificially raise rolling resistance a lot so the moving tarmac can have a noticeable effect.
This BS always stems from people's lack of understanding how a plane flies. As an engineer and former pilot, it drives me absolutely bonkers knowing that people honestly think that wheel speed has literally anything to do with it. Flight is always bound to airspeed against the wings and has nothing to do with wheelspeed.
There are two versions of this question. One where the treadmill matches the speed of the wheel, and one for matching the speed of the plane.
and neither change the answer meaningfully.
"Take off speed" is all about the air flow speed over the wings. That is why you better damn well have good tie-downs for a Cesna. :)
Or a cub.
Air-speed vs. Ground-speed.
One matters to keeping the plane aloft, the other doesn't.
@@ericgulseth74 More like one matters to keeping the plane aloft, the other counts to how hard the impact of touchdown will be.
@@g00gleminus96 You are thinking of descent speed. With a ground speed of 0 a plane could land without you knowing as long as the pilot can control the descent speed.
@@ericgulseth74 How 'bout an Antonov AN-2? Give it a 35mph headwind and it can achieve a ground speed of -5mph.
So, the wheels on the plane are basically just bearings. Their only role is to reduce friction with the ground. (As much as possible when taking off, and in a controlled fashion when landing)
And to hold the plane up off the ground. Just supports trying not to hinder forward movement.
Need to interject here. While the experiment showed that the plane would take off, the experiment itself was fundamentally flawed, and I'll explain why in a few lines. This is not a dig at Adam whatsoever. But in order to answer the question portrayed, the details have to be absolute. No new variables or flawed math, intentional or not.
The wheels and the conveyer belt are the ONLY variables that matter and I'll explain why in a few lines. It's a fundamental physics problem. It does not matter if the wheels and engines are mechanically connected or not. Adam is a great educator, actor, tv host, etc., but he is not a scientist or engineer. It's not a problem of if the plane can reach a speed to take off. Obviously a plane needs ample amount of lift to take off .It's a problem of if the plane will move whatsoever. And the physics of the problem stated does not allow the plane to move.
This is COMPLETELY wrong, and I wish he would just go do more research instead of sticking with his guns in the "my experiment proved it so it cant be wrong." fashion. I grew up watching Myth Busters and absolutely love the show, but experiments do not always provide correct outcome if the variables are not perfect and if external variables are added.
The mode of force, tires vs propeller/engine are irrelevant. The ONLY variables that matter are the wheels and the conveyer belt. It doesn't matter if its a propeller pulling, an engine pushing, the wheels mechanically turning, a person off the conveyer belt pulling, any of that. If you tied an infinitely strong rope to the front of the infinitely strong hull of the airplane and applied an infinite amount of force, you would not be able to move the plane. The only thing that would happen is the wheels and conveyer belt would reach an infinite speed.
This concept is so hard to grasp because it's out of touch with reality. 99% of physics questions taught in classrooms happen in a perfect hypothetical world, and could not exist in the normal world. And if they did, the results would be drastically different. This is one of those questions. There are two main reasons that the experiment that you did were flawed.
1a. It is impossible to instantaneously match the speed of the tarp and the speed of the wheels on the plane.
1b. As the plane tries to take off, the acceleration of the truck needed to accelerate match the planes speed. Going the same speed as the plane is useless. The math does not add up.
2. The tarp that you pulled was also in contact with the ground and not supporting the weight of the plane. Thus, the plane was able to use the ground underneath to help propel itself forward.
It's even impossible to replicate the perfect experiment no matter how much money you throw at the project. So you have to rely on fundamental physics to figure out the problem.
Breaking it down fundamentally.
If the circumference of your tire is 1 meter, as the tire rotates, the conveyer belt moves back 1 meter, matching the speed of the plane's tires instantaneously. In order for the plane to move horizontally, the tires have to rotate. And the tires cannot rotate without the conveyer belt moving the opposite direction the same distance at the same speed.
The issue is ground speed and air speed. With enough "wash" from the propeller, can enough lift from the wings be so generated. I guess it depends on the design of the aeroplane.
People forget that in tornadoes and hurricanes, or even wind storms, light aircraft that arent chained down will take off and glide around uncontrolled. This is because lifting the wings causes takeoff, not groundspeed.
also a way to actually force a plane to stay grounded is tailwind. if you could produce a direct tailwind equivalent to the takeoff speed, the plane would stay grounded.
I thought the controversy was people thinking that the conveyer belt was rolling backwards so fast that it created enough friction in the wheel bearings that it prevented the airplane from moving forward with thrust from propellers.
Thats where the phrase "matches the speed of the plane" lets us down. It doesnt make clear what speed thst means.
That's the semantic ambiguity in "as fast as the plane is moving forward". In the 25 tarp/25 mph ultralight experiment, just before takeoff, the wheel speed was 50 mph. If you believe the semantics of the question then require that the tarp must be accelerated to 50 mph, because that's how fast the wheels are rolling, then the wheels will see 75 mph (and yes, slightly increased wheel bearing friction), and the tarp speed must be increased again, until something breaks.
@@kevinvermeer9011 the question doesnt say anything about how fast the wheels turn.
This is it exactly. Take 25 mph as the take-off speed. If you somehow engineered the wheels to be incapable of turning faster than the equivalent of 25 mph, and assuming the plane wasn't powerful enough to drag itself forward with locked wheels, it would never move forward on a 25 mph treadmill. Of course, that's not how wheels work.
The ambiguity in the language is the key. The question the "no" crowd actually has in mind is "can a plane take off without moving forward?" They're taking it for granted that the treadmill is a means to prevent the plane from moving forward, but that's not the actual premise. The question being tested here is "Can a treadmill spinning at 25 mph prevent a plane from moving forward?"
The way to test what they have in mind would be to tie a chain from the back of a plane to a pole fifty feet off the ground.
@@kevinvermeer9011 Exactly, and it seems like even Adam is still confused about this. What you're describing is the same version of the question that prevents the car from moving. So, if it's true that the car can't drive, then the plane moving forward would instantly make its wheels spin up to infinity.
In the version they tested (the conveyor moving backwards at the speed of the plane's body) the car actually can drive forward. If the car drives at 25 mph, the wheels' experience would be the same as driving normally at 50 mph.
I totally forgot that the wheels aren't creating the traction for an airplane. D-u-umb
me too i totally was on side "grounded" but i now feel smarter knowing the truth.
@@nyrmotworyk Until we forget it again... Lol
Yep. Imagine if you could drive the plane's wheels with say, an electric motor, and propel the plane along like a car to takeoff speed. If that were the only mode of propulsion, the plane would reach takeoff speed and take off, at which point the wheels would lose contact with the ground and no longer be able to sustain the plane's forward speed. Then the plane would slow down due to aerodynamic drag and come back down, at which point the wheels would contact the runway again and speed the plane back up to takeoff speed and it would take off again. I guess the plane would move along in a series of hops if it were driven this way, unable to sustain sufficient airspeed when off the ground.
I remember thinking it was kind of dumb since the wheels aren't the motive force, i thought it was kind of obvious from the start. didn't know about the controversy until now.
@@mrfancypanzer549 For someone who knows about airplanes enough to see that clearly from the start, it must seem dumb, I agree!
Imagine a plane taking off on ice with the parking brake set. Wheels never rotate but it still slides down the runway and takes off when airspeed is high enough.
What if the ice was a block of ice going downriver in a current accelerating at the exact speed the airplane was accelerating at? Ha!
The whole debate comes from the wording of the problem. The variable that doesn’t change is wheel speed to treadmill speed which is equal in the problem. Only IF the wheels travel faster than the belt will it lift off.
I love the "we" you always say about the team. Any time he references Jamie, the word genius follows. He lights up talking about Grant & Co. Love it. Makes my entire childhood worthwhile. Mythbusters is half of the reason I watched Discovery, and half the reason I got my degree in science.
Whats the other half if you dont mind me asking?
@@ampadedoda5027 explosions
@@austinbrunette8773 Best answer you could have given.
That's awesome. Last week I posted that if Adam had been my science teacher I'm sure my career would have been very different. Unfortunately we're the same age. I'm glad you were able to take advantage.
Congratulations
Jamie will always be one of my favorite people just because of his ability to be so blunt like when Adam said "I took it to Jamie and he said why would we do this? It's stupid"
The mythbusters actually got this one wrong, if you dive into the real original question.
@@hautehussey how
@@5hiftyL1v3a because such a treadmill would be impossible to build in real life. The only real test they could’ve done would be to fuse the wheels completely and then seen if a plane could take off!
@@hautehussey The Mythbusters did not get this one wrong. They simply answered a different question than you are answering. There is two versions of this myth. One is testable and practical. The other is not testable, and quite frankly, a broken question.
@@GamingVids1984 you don’t get to change the question just to make it easier to answer. That’s Trump supporter logic! But yes, they should’ve spent more time discussing the question, including in this video.
Good breakdown. I'm not sure why there's so much debate around the principal. As the type of aircraft in this myth was a propeller (prop) plane it doesn't rely on the transfer of energy from the gear to generate momentum, it uses the thrust generated by the propeller to push air back (over the wings) and propel the plane down the runway. There's only 3 potential scenarios I could think where takeoff wouldn't be possible 1) if the resistance of the tires was so severe that it prevented the plan from getting enough speed to generate sufficient lift, 2) the belt interrupts the flow of air in front of the aircraft, 3) you attempt this myth with a tailwind, which are often great to have, just never at takeoff.