airplane treadmill mythbusters
Kevtastic said, “You immediately violate the rules of the question and the experiment if, at any time, the wheels move at a different speed than the treadmill, which is the only way the airplane could gain relative air speed and lift.” It should be obvious that if the plane moves faster than the tread mill, it will run off the mill and roll onto solid tarmac, probably catastrophically.
Since the plane isn’t moving in the slightest, the wheels are only spinning because the treadmill is, and vice versa. You could literally hold the airplane still with one hand though, and in that case its wheels would spin.
If you can prove that the minimal force being transfered to the plane by the interaction of the wheels and the treadmill will be enough to prevent the airplane from taking off, I will have no choice but to concede. is not enough to do so.
If you understand the forces taking place when an airplane takes off you know that even if the treadmill is travelling 10x faster than the wheels or the plane, the plane will still take off.
A treadmill could be built that would blow out the tires and ground the plane that way, but there’s no way to generate enough rolling friction in airplane wheels to stop an ordinary plane moving forward without damaging it. If you get to specify the plane and the treadmill, though, I agree that it’s possible ” a tiny model plane on a bumpy treadmill moving at 500mph would not take off, for instance.
Option A: Factor in friction: With friction in play, the treadmill can’t accelerate quickly enough or to a high enough speed to hold the airplane still. It doesn’t make any difference if it’s sitting on a treadmill or not.
Basically it doesn’t matter how fast the treadmill is going it is not a factor in the forces necessary to move the airplane.
The treadmill is not connected in any meaningfully solid way to the aircraft. It has no method of acting with enough force on the airplane to keep it still.
Rolling friction is not a reasonable way to hold an airplane in place, even if we postulate a magic treadmill.
Ace, Jeremy, Jeff, and Ormerodp, you all are making the assumption that the treadmill will hold the airplane in place. If the treadmill did counteract the forward motion of an airplane than it would be impossible to take off on an icy runway.
Enginerd, the problem is that you’re placing the treadmill in an “ideal” model and the airplane in a “real-world” model. If you have to factor friction in, you have to factor it in for both components of the equation.
Option B: No friction: No matter how quickly the treadmill spins, it won’t cause any slowdown of the airplane, so obviously the airplane will take off.
The essence of the question is whether or not a treadmill can prevent an airplane from taking off.
The airplane treadmill seems to generate a lot of debate b/c the problem is poorly worded and generates confusion.
If you don’t specify that the treadmill must keep the airplane stationary, then the problem is trivial.
How absurd is it to think that the treadmill will not pull back on the airplane harder the faster it goes.
Jeremy, not only that, but like I said, it’s sort of disingenuous to give the treadmill ideal bearings and unlimited power but then grant the airplane limited bearings and power.
Alas, the wording on the puzzle has gotten a little munged up, saying that the treadmill matches the wheel speed. The outcome of the Mythbusters test is going to rely on which question they actually tested, since there are two questions with very important differences.
If the Mythbusters explanation that the wheels on a plane don’t matter is correct, then I don’t see why even a car with finite power can’t accelerate to an arbitrarily high forward speed over a treadmill moving backwards with any constant speed, no matter how great, provided there’s always enough friction to keep the wheels rolling without slipping.
There isn’t a plane in the world that can generate enough wheel friction to match that thrust, because the axles will catastrophically fail before reaching that. as soon as the treadmill was removed, the plane would accelerate down, and into, the bow of the aircraft carrier that was so bold to experiment with our brave men.
At one place, Mythbusters state the question as plane going forward at take-off speed and treadmill going backwards at take off speed. Now I’m really hoping the next version will have atleast one airport with a really large treadmill and an option to set it’s counteracting speed to either the fusalage or the airplane wheels.
The upshot is that if the experiment were performed ideally, then the speed the wheels are turning would be exactly twice the speed of the airplane as the wheels left the treadmill .
Nor is the treadmill exerting any force against the plane - the plane’s freespinning wheels make sure of that.
The treadmill cannot slow down the airplane, so it accelerates to the speed of light, time comes to a stop and the universe implodes.
A reasonable substitute for the treadmill. First up, for those concerned that this story has been cancelled, don’t worry, planes on a conveyer belt has been filmed, is spectacular, and will be part of what us Mythbusters refer to as ‘episode 97′.
Browsing the Mythbusters wiki, it’s amazing to see how many people think that the myth is “If you keep the plane from moving, can it take off” instead of “can the treadmill keep the plane from moving”.
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There is another flaw: in your interpretation of the problem, the moment the plane’s engines overcome the static friction of the wheels, the treadmill will instantly accelerate to whatever ungodly speed is necessary to create enough rolling friction to stop the plane . If in fact the plane did start to roll forward against the treadmill, then we would have a logical paradox because the question states that the treadmill must match the speed of the wheels. How the treadmill accomplishes this I’ve explained many times over, but really the question contains it’s own answer when you assume that it won’t contradict itself.
If you set a plane on the treadmill and push the throttle to 80mph , the treadmill will roll backwards at -80mph, and the plane will zip forward normally at 80mph, with the wheels spinning as if it were moving at 160mph. That’s the difference, and that’s what the question is examining: the fact that planes don’t push against the ground, so treadmills don’t affect them.
The treadmill is designed only to match the speed of the wheels, not to hold the plane in place. The plane will accelerate forward and the treadmill will adjust its speed to match that of the wheels.
Please just please just please tell me how the premise of the question can hold true if the plane takes off.
The speed it achieves will be unrelated to the treadmill, because the wheels are only there to keep the plane from damaging itself while on the ground.
The thought experiment says NOTHING about the motion of the aircraft with respect to the ground. “A treadmill does not move the air around it except for a minuscule amount against its surface.
A treadmill has no good way to stop a plane moving relative to the air. The wheels spin freely, and so long as they’re in contact with the treadmill, they will travel exactly the combined speed of the forward motion of the car, plus the reverse motion of the treadmill.
If in fact the plane lifts off, it has clearly generated sufficient lift to overcome gravity, and after losing contact with the ground, the treadmill and wheels will have absolutely no effect on the plane’s flight.
You start the engine and the plane begins to accumulate forward momentum but it doesn’t move with respect to the ground because the treadmill applies an equal but opposite force to the plane’s forward momentum.
You run into the chicken-and-egg problem I mentioned above .
The treadmill can go 200 mph backward while the wheels go 200 mph forward and the plane still goes 0.
The wheels /can/ move forward. You are on the wrong side of this argument.
As long as we’re not jumping into lala land with theoretical instantly accelerating infinite speed capable treadmills that melt the tires, wheel bearings, landing gear, and finally the underbelly of the plane, the plane will move forward just fine.
If you pull MORE on the bars, you have the potential to move forward, but ONLY if the treadmill does not speed up. He asserts that there is some other force holding the plane stationary BEFORE any thrust is applied, and that is just not true.
“The force necessary for takeoff cannot be acheived when the plane is stationary as it would be on a treadmill which is moving at the same speed as the airplane.” If you have any scientific credibility yourself you’ll watch this video.
The wheels are still moving at the same speed as the treadmill, and yet the car can move forward because of your external force that isn’t influenced by ground speed.
The treadmill thing means the plane isn’t actually moving - just it’s wheels are. You can stand right next to a planes that’s thrusting it’s ass off while on a treadmill.
If you postulate a magic treadmill that somehow can hold the plane in place, it won’t take off; that’s not the intent of the original question, and as a physics puzzle it has serious flaws.
In the same way, the plane engines, pushing against the air, won’t be much bothered by the treadmill ” that’s the point of the puzzle, to demonstrate that cars and planes are sometimes different in counterintuitive ways.
Unless you change your frame of reference from absolute speed to speed relative to the treadmill when you switch from plane to car, then the plane and car behave absolutely the same, save for the fact that cars can not actually fly.
Now if the problem has the treadmill moving at the speed of the PLANE, then the plane could take off.
If you want the treadmill to speed up infinitely but not the plane, you are adding variables to the question. The “treadmill” can already accelerate to infinity, but you want this to be impossible for the plane.
However if the plane is held stationary w.r.t to earth by increasing the speed of the treadmill it is still possible for the plane to take off because the treadmill will push the air too creating a sort of wind tunnel.
It all comes down to: does the treadmill go at a fixed speed inverse to the plane’s normal land speed , or do they accelerate to compensate? As soon as the plane starts to move forward at all , the wheels and the treadmill will both immediately accelerate to infinity.
Nevermind the ideal characteristics of the treadmill, or the wheels, or whatever. A treadmill does not move the air around it except for a minuscule amount against its surface.
If I put a red wagon on a treadmill and start the treadmill at 1 MPH, it’s going to try to pull away from me. It will not apply an equal magnitude opposing force, but will just add a bit more friction.
Your forward motion won’t be significantly impaired by the treadmill, since roller skate wheel bearings are a crappy way to transmit frictional force to your body, and that’s all the treadmill can do.
My assumption all along was that the tread moves because its motors are moving it along. That’s vertical flight anyway.Bottom line, in the experiment as described, the plane will not fly.
The propeller/jet will move the plane forward whether or not there is a treadmill underneath it.
The question asked does not specify that the plane sit still. It specifies that the treadmill moves.
The question doesn’t ask if the treadmill can keep up with the plane wheels.
If we assume that the wheels on which the plane rides are somewhat ideal, i.e. frictionless, then whether or not there is a treadmill or conveyer belt has nothing to do with the problem.
At any point, if the plane starts moving forward and the wheels are still in contact with the treadmill, then the wheels will have to be moving faster than the treadmill. At that point, it’s not about physics anymore, it’s about semantics.
Consider the inverse: if the plane isn’t moving forward, then it follows that the wheels aren’t moving and the treadmill isn’t moving either.
The whole idea here is that the plane is moving very fast with respect to the treadmill, but at zero velocity with respect to the ground and the surrounding air .
If you assume the plane won’t take off, your model assumes that if i had a plane on a treadmill attached to a rope tied to the ground, I could break the rope by running the treadmill fast enough. That is missing the point.
You see, if the wheels and treadmill do not spin at the same speed, then we have a contradiction with the premise in Point A.
Buy yourself a Hot Wheels and put it on the rail of the escalator and hold it in place. The wheels are moving the same speed as the treadmill, obviously, since they’re in contact.
Whether the treadmill is crawling at 5mph or zipping along at 50mph, the force required to hold your red wagon in place is the same. That is a daunting task.
The question states otherwise in the case of the treadmill, but not in the case of the plane.
The argument that the treadmill itself will cause drag on the air, causing wind, causing the plane to take off is partially correct.
If the intent is for the plane to stand still, the treadmill is useless. It would be just as effective to say the brakes were on and keeping the plane from moving.
I guarantee you that if you stand on your treadmill with roller blades on and turn it on, you’re not going to go backwards as quickly as the treadmill is moving. If you hold onto the treadmill’s bars, you won’t have to grip it with as much strength as your weight would ordinarily require: because the treadmill isn’t applying force directly to you, it’s acting upon the wheels which are light and isolated from you by good bearings.
What this says, is that the less force it takes to turn a wheel, the faster the treadmill will have to move backwards to counteract the power generated by the engine.
If the treadmill is going 5 MPH backward, then the wheels are really turning 10 MPH forward.
If you’re hauling yourself forward at 1 m/s, the treadmill will roll backward at 1 m/s, and your roller skate wheels will be freely spinning at 2 m/s.
The wheels and treadmill arrangement are posited so as to instantaneously counteract and eliminate any forward thrust provided by the engine.
As the wheels are not coupled to the engine in any meaningful way, the treadmill CAN’T counteract the thrust of the engine. The conveyor belt is able to react to any changes in speed, instantly, and the microsecond the thrust of the engine tries to push the airplane forward with any speed , the conveyor belt will accelerate to that speed, the wheels will accelerate , the conveyor belt will accelerate further and so on, towards the speed of light.
Lets say the thrust of the engine gives the airplane an airspeed of 30 mph , and holds that speed. Its groundspeed will also be slightly slower than normal .
The wheels are irrelevant to an airplane’s forward motion and are present to reduce friction between the plane and the runway.
Simply put, the wheels on an airplane act as a lubricant between the plane and the runway.
Example: Wooden rubber band powered airplane. If it’s too short, the plane will run off the end of the treadmill.
Flick on our hypothetical massive treadmill, and the plane might or might not roll backwards a bit.
Jeff, Of course the treadmill has to be as long as a runway for the plane to take off from the treadmill - that’s clear.
You might want to re-read my answer ” I agree with you! The plane will take off, just as someone wearing roller skates on a treadmill will move forward if they pull themselves forward using a rope.
When the treadmill matches/is identical to the speed of the PLANE, the wheel speed is essentially double the individual speed of either the plane or the treadmill.
Enginerd, you seem to be missing a pretty fundamental flaw in your analysis: rolling friction does not increase with velocity. The answer is nothing.
The only air that’s moving is caused by the propeller, other than the “hug” air that is dragged along the treadmill surface due to micro vortices caused by the friction of the tread next to stationary air.
If it were possible to match the power generated by the engine by a moving treadmill would there be any air movement over the wings.
I say yes, but only because the bearings in the rollerskates aren’t ideal.
If you were to put a real aircraft on a real treadmill that really traveled the same speed as an aircraft taking off, only in reverse, the aircraft would take off.
Unfortunately, the treadmill exactly matches your speed in the opposite direction.
Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed.
Questions about whether the treadmill is ideal or practical, whether it accelerates infinitely or can keep up with the wheels, whether the wheels catch fire or not - beside the point.
No, the “super treadmill” question may not be as interesting to you as it is to me. The plane’s forward motion is provided by something that doesn’t touch the ground, so being on a treadmill doesn’t make any difference.
You, as a person, use the same amount of force to push the car forward, no matter if the treadmill is on or not.
When running on an exercise treadmill we stay stationary relative to the room because the force generated by our feet pushing against the treadmill belt is not transfered to the floor.
The MTOW and runway length required may be different, but assuming an aircraft that is not overloaded, it’ll fly. If the treadmill matches PLANE speed, then the treadmill can go 100 mph backward while the plane goes 100 mph forward and the wheels spin at 200 mph.
The question states that the treadmill matches the speed of the wheels. That is the only constraint, and it implies that the treadmill is in fact an “ideal” model of a treadmill.
Enginerd, the original question does indeed posit that the treadmill matches the plane’s forward speed ” or, more precisely, the forward speed that it would have had without the treadmill.
In this example it isn’t connected to the treadmill and you stay put.
If we were to strap on a Buzz Lightyear rocket pack while running on the treadmill and light it off, it wouldn’t matter how fast the treadmill was going because the rocket would be pushing against the air and away we would go.
At some point the treadmill will be going fast enough that I can’t hold on, assuming I can get the treadmill going fast enough.
Now, hold on to the bars with your arms, as the treadmill moves beneath you.
If you stick wings on a car and set it to rolling on a treadmill at 80mph, the treadmill will roll backwards at -80mph, and the car will be stationary at 0mph: it won’t take off.
Where I was initially led astray was that I assumed that the force of the treadmill matched that of the thrust.
A treadmill going 100 mph one way will not balance 100 mph’s worth of thrust in the other way.
We can use physics and math to explain WHY that is and HOW the treadmill counteracts the thrust of the engines.
The treadmill will only go as fast as force of the propulsion is pushing it.
For a visualization of the forces in place it is best described on The Straight Dope The Straight Dope : “Imagine you’re standing on a health-club treadmill in rollerblades while holding a rope attached to the wall in front of you.
There’s nothing magical about it, it’s simple physics.
Worth noting is that when the car starting moving forward from “thrust,” the wheel speed no longer matched the treadmill speed , violating the rules of the version of the question that requires the treadmill matches the WHEEL speed.
If the wheel speed exactly matches the treadmill speed at all times, forward motion is thereby defined to be impossible ” not a very interesting puzzle, and not something that makes a lot of real-world sense re: treadmills.
MythBusters tackles “plane on a conveyor belt problem” - Boing Boing MythBusters tackles “plane on a conveyor belt problem” Last night I spoke to Adam Savage, co-host of MythBusters.
For this MythBusters example the plane is a prop plane and it will not move forward because a prop generates forward momentum by the screw action of the propeller.
Mythbusters is going to mix it up with the use of a full-scale prop plane, but the physics are the same.
Oh, and while I do like the idea behind Mythbusters, and the people involved, they have a lot of problems with the setup of some of their experiments. Airplanes fly because of lift, which is created by relative movement of air past the wings.
There’s a conveyor belt, there’s an airplane, and there’s air, nothing more.
The plane moves in one direction, while the conveyer moves in the opposite direction. If you consider the only two components, and how they interact, you realize there’s no way for the conveyor to keep the plane stationary.
A conveyor belt cannot act against an airplane in any manner to prevent it from moving forward and achieving lift.
The airplane is free to move forward regardless of the longitudinal motion of the ground beneath it.
The airplane will accelerate and move forward just as if was on motionless ground and it will take off.
It is IMPOSSIBLE for conventional airplanes to take off without great forces of wind pushing on the bottoms of their wings.
Nowhere in the question does it state that the airplane remains stationary/motionless.
Clearly you are still under the misconception that an airplane and a car work the same way.
Now, an airplane is going to have a hell of a lot more mass and thus resist being put into motion more. The force it takes to push your roller skater along the treadmill increases as the treadmill speed increases.
The original question floating around for years and years and years has always been about whether the treadmill matches the PLANE speed. If you think the plane can take off you generally think the wheels are absolutely frictionless When the treadmill starts, the plane doesn’t move becausethe wheels turn byt themselves, therefore allowing the thrust of the engine to devote all it’s power to moving through the air and taking off.
The treadmill has nothing to do with it plane. You can’t apply a force through an ideal free wheel.
The treadmill can move with an opposing speed to the plane, but it cannot apply an equal and opposing force, because wheel bearings transmit only a very small rolling friction.
A treadmill does not measure it’s speed relative to objects on top of it, but on how fast it’s surface is moving relative to the Earth.
As the treadmill picks up speed , it begins to slow down the plane not by wheel friction, but by wind, the same wind that gives planes lift.
To provide 180hp of “drag” through the spinning wheels, you’d have to spin the treadmill at some ungodly speed. I suppose on some aircraft this would exceed the tire speed limitations and cause a blowout.
If you believe that a treadmill moving in the opposite direction of a plane at a speed equal to the speed of the plane will prevent it from moving forward, I’m assuming you believe that the speed the wheels are spinning at can counteract the force of the plane’s propeller.
How, the plane is accelerating forward and the treadmill isn’t exerting any force to stop it? I say that you just need a powerful enoguh engine that will blow enough air over the wings.
The treadmill can spin as fast as it wants - the plane’s freespinning wheels will just spin faster - but the plane itself will continue to pull itself through the air. All the treadmill has done is make the freespinning wheels spin twice as fast as they otherwise would have.
The treadmill could go 1,000 MPH and it would not matter, the plane will not move backwards as the plane’s wheels are free to spin and match the treadmill.
Matt, correct, and the point that I was trying to prove was that IF the treadmill somehow got fast enough, and you had crappy bearings in the wheels to provide enough reverse friction, it WOULD hold the plane back.
The plane does move forward - regardless of whether or not there’s a treadmill moving in the opposite direction below it - because the forward movement of the plane doesn’t rely on the free-spinning wheels. It relies on the propeller, which propels the plane forward no matter how fast the free-spinning wheels are spinning.
Ditto for the speed of the treadmill.
At what speed does the plane start moving backwards? Their issue is that the speed of the plane should be measured relative to the treadmill, and that the speed of the treadmill should be measured relative to the ground.
Just like running on a treadmill, or driving a car on one, if the speed of the treadmill is matched in real time to the forward speed of the person or car then surely there will be no movement relative to an observer on the ground.
A treadmill can keep a jogger, or a car, from moving forward, because joggers and cars generate forward motion by pushing against the ground. A plane doesn’t generate forward motion by pushing against the ground - it generates it by using its propellers to move air.
If you think the plane cannot take off, you assume that as soon as the treadmill starts, the plane moves backward and thrust must be used to simply keep the plane stationary in relation to the ground.
If the bike/plane does move forward, that would mean it’s wheels either slide or they revolve faster than the treadmill.
I’m I right in thinking that if the hypothetical treadmill is turned on before the planes engines are fired, then the essentially friction-free, free-spinning wheels will just turn and the plane will remain static .
A 2ft diameter plane wheel going 25mph spins at about 350 rpm. The treadmill would have to go about 10 times faster than that to begin to push the bearing past its working zone and begin to create any frictional forces which can slow down the plane.
No matter the speed of the treadmill, it can never impart any force to the plane other than a tiny constant rolling friction.
Bolt the plane into position on a treadmill and speed up the treadmill to 60mph. Now, turn on the engine and release the bolts.
Measure how much longer the plane would need to travel to gain enough speed to lift off along the treadmill.
The wind speed will become high enough that it will lift the plane up before the treadmill melts the bearings.
If you start with the assumption that the treadmill will keep the plane from moving forward, then no, the plane won’t take off. It both demonstrates that the plane will move forward regardless of the treadmill , and negates itself by saying the treadmill will keep it in place, when the treadmill has no say in the matter. that if you follow the myth exactly, the plane is actually not moving at all, therefore treadmill is not moving at all.
However there is no way in the world given that a airplanes wheels by definition have to have virtually frictionless bearings that the conveyor belt could exert enough force on the plane to prevent the thrust from the engines from moving the plane forward with respect to the ground and the air.
In a related matter, an airplane WILL lift off the ground - it will technically “take off” - while standing still on the tarmac, provided there is a fast enough stream of air blowing over the wings. It’s the plane’s motion relative to the AIR that matters.
I had a feeling that the long awaited Mythbusters episode wouldn’t end the debate once and for all because the people who interpret the question as being a situation in which the conveyor belt keeps the plane stationary with respect to the ground and thus the air will always believe that the experiment has been done wrong.
On MythBusters, the plane was going 25 MPH to the right, the tarp 25 MPH to the left. In my vividly exaggerating imagination, the sort of people who’ll fly a plane without really understanding what keeps it up there are also the sort of people who’ll put their poddle in the microwave in order to dry it after a walk in the rain.
The Mythbusters workaround was clever, but not analogous, since the plane clearly was not stationary relative to the ground.
The harder the plane’s engines push, the faster the treadmill moves, and if the bearings can hold out, the more lift the plane will get, eventually getting airborne and taking off.
The treadmill can go 1000 mph and it still can’t stop the plane. and the plane takes off.
The treadmills pointless, the myth is a pandora’s box condundrum piece of crap that was made to piss you off, leaving us with the original statement that i said, which was “can a plane take off with no forward movement”.
Does the treadmill suddenly start moving? Now, with the plane still flying 100 MPH into the 100 MPH headwind, stationary on the treadmill, start up the treadmill accelerating slowly.
We’ll say at 250 mph the treadmill can start to slow down the plane .
Just like with the skateboard the plane has access to something that isn’t moving with the treadmill.
You can’t have a frictionless treadmill without frictionless wheels on the plane.
The only connection between the aircraft and the treadmill are the wheels of the plane.
OK, imagine a frictionless set of wheels on an infinitely long treadmill. They start the conveyor belt, and assuming no friction, nothing happens.
I was thinking this morning that they should have also shown the model plane with no wing on the treadmill.
If the treadmill was moving forward or backward at 100mph then the plane doesn’t move, at 500mph, the plane doesn’t move etc etc.
You’re missing the point - the treadmill DOES NOT - CAN NOT - keep the plane from moving forward.
No matter how much more thrust is applied the treadmill is cranked up to match and the plane never gets lift.
Here is the lift problem simplified: You get in the plane on the runway instead of the treadmill.
It only that it moves in the opposite direction at the same speed.
Under the frictionless model, you won’t even need any additional thrust to reach takeoff speed, as the only thing the treadmill affects is the speed the wheels spin at.
My cycle’s tires are propelling me forward against the surface of the treadmill, but the surface of the treadmill is moving backwards at the same speed, negating my progress. Now, consider this.
I wasn’t paying complete attention while watching the show, but I’m guessing that we are all arguing slightly different myths, but the main one in contention is a super basic one stating that the “treadmill matches the forward speed of the plane.”
In general, pilots are far more interested in airspeed rather than ground speed, for obvious reasons. how much “drag” does the treadmill place on the aircraft.
The treadmill exerts no force on me at all - my freespinning wheels allow negate it completely.
You can’t have the plane moving , or else the treadmill is going slower than the plane . You can’t apply a force through an ideal free wheel.
My free-spinning wheels will spin faster , but I can still pull myself forward with the handrails, with minimal effort.
There’s a handrail on either side of the treadmill. The treadmill is rigged so that it moves as fast as the bike’s wheels move, but in the opposite direction .
The only problem with your analysis is that the car’s speedometer will read relative not to the earth but to the treadmill, as that’s what it’s wheels are touching.
I’m a pilot too, and unlike that other guy it’s readily apparent that the plane would take off from a treadmill.
The treadmill is then immidiatly accelerated to a speed that is equal or higher then the take off velocity of the fighterjet.
You would begin to move forward, but again we run into the problem of the treadmill trying to hold you in place. It can’t.
Standing on the ground next to the treadmill, you place the skateboard on the treadmill and hold on to it.
As everyone else notes - the ground doesn’t matter, hence the treadmill doesn’t matter.
If this treadmill is very long and very wide, we can assume laminar flow over the surface.
Since fluids have a no-stick condition at the surface of the treadmill, the treadmill will pull air along with it. A fighterjet then positions itself on one end of the treadmill and stops.
I can see the argument that “the planes movement forward must equal the treadmill speed moving backward.”
If you want to get silly with it, as the treadmill speed instantly approaches the speed of light it creates a layer of super hot plasma and generates more heat energy than a thousand atom bombs, vaporizing the plane and sending everything in the area high into the air .
The original questions does NOT say “the conveyor belt pushes backwards on the plane”. The propulsion of an airplane does not originate from the wheels but from the air pressure and air speed produced by either a propeller or a turbine as in a jet engine .
What is relevant is the plane’s speed relative to the air .
What really happens is that wings deflect air downwards, which results in the equal but opposite force known as lift. They irradiated them and most of the roaches died.
The wheels have nothing to do with the thrust of the airplane , and the conveyor belt cannot exert any thrust on the airplane .
You can run the conveyor belt at any speed you like .
Then you remember the differences between how cars and airplanes are propelled, and you realize that a conveyor belt would have no effect on an airplane, just as it would have no effect on someone wearing roller skates and a jet pack, or a car in neutral rolling downhill, etc.
REWARD - to anyone who can build a conveyor that will actually hold the airplane stationary.
Instead of riding it, I stand to the side of the treadmill and hold the bike upright with my hands.
No matter how fast the treadmill moves, if you pull on the chain, and the chain gets shorter, you will move forward.
An Internet debate ensues. Other people regard this criticism as stupid, because anyone knows that treadmills hardly affect the use of phones.
If you assume that plane speed is relative to the treadmill, then, the plane does not take off.
You have a choice, the physically impossible paradox of measuring plane speed against the treadmill, or the commonly accepted definition of speed .
If you agree that you can roll a skateboard around on the treadmill pretty much however you like regardless of treadmill speed as long as you have a good grip, then consider this: A plane’s engines work pretty much the same way: they “grab” onto the air and pull it forward.
Presumably, the treadmill’s speed will be adjust so that no matter what the cars speedometer is reading, the car will not actually be moving relative the earth.
You want the speed of the belt’s surface relative to the ground to be the exact opposite of the speed of the plane relative to the belt’s surface. They could have at least acknowledged the other reading and not accuse everyone who doesn’t think the plane will fly of thinking a plane is a car- that’s just silly.
I find it amazing that the mouth breathers that actually thought the plane would not take off are still arguing that it won’t take off even AFTER IT HAS BEEN PROVEN by both MythBusters and the simple law of physics.
I have flown planes similar to the one in mythbusters and I am also majoring in physics, so I hope I can provide some insights.
less, AIR has to move FAST ENOUGH over the wings. Ok, I wish the mythbusters did THIS experiment which would pretty much put this to rest.
Mythbusters’ experiment proved nothing, it took off because the plane’s speed overcame the pickup’s opposite direction speed and moved through air allowing lift.
Still think the Mythbusters experiment sounded flawed. In that case, it’s pretty clear that I wouldn’t move forward.
The plane speed relative to the treadmill will equal the plane speed relative to the ground + the treadmill speed. That has to equal the treadmill speed.
The condition that the plane speed equal the treadmill speed implies that the speed of the plane and the speed of the treadmill cancel out and the speed of the plane relative to the Earth is 0.
If that causes your head to spin, just think of it this way: All the treadmill does is cause the wheels to spin faster; it doesn’t move the plane backwards once the propeller starts moving it forwards.
If you nitpick and claim that the speed of the treadmill must be equal to the speed of the wheels, then you are simplifying the problem to something else, which is If we prevent the plane from moving, will it take off? One way to completely put this myth to rest and be busted is to place a glider on the treadmill.
The first is that the plane’s thrust is delivered via the wheels to the ground - that the wheels are what is causing the plane to move forward. This is the case when you put a car or a human on a treadmill.
Once the wheels start spinning, the backwards force acting on the plane from the treadmill will be so small relative to the forward force from the propeller that the plane will start to move forward.
Let’s ignore air resistance for simplicity’s sake since it doesn’t play a significant role. People nitpick and so we add in all sorts of details: the treadmill moves backwards at exactly the same speed as the plane moves forwards ; the treadmill is infinitely long ; and of course, the most controversial addition, intended to imply that the plane does, in fact, have wheels: the treadmill matches the speed of the wheels.
I love this question, but it amazes me to no end to see the multitude of different ways that people can misinterpret the question. That’s the question, in it’s simplest form.
The planes GPS will show the same speed needed to take off everytime, doesn’t matter if a treadmill is under it or not.
@Troy: They measured the plane’s take-off speed with the plane on a normal runway, and then drove the truck at that speed. They never actually measured the plane’s speed while the plane was on the treadmill.
Tape a handheld GPS to the belt on the treadmill, tape a handheld gps on the plane.
I would agree with the previous poster’s hypothesis that the wheels are simply spinning fast enough to match the pace of the treadmill, with no real airflow over the wings.
If there was a separate treadmill under each wheel and a vertical pole through the aircraft so that it could not move forward but only up and down, no matter how fast the treadmill was going or the propeller spinning, the a/c would not take off.
Tie a rope to the nose to stop it from moving backward and start up the treadmill. They did not even truly match the speed of the conveyor to that of the plane: The conveyor’s speed was based on the wheel speed of the truck pulling it, where the airplane’s speed was taken from the pitot tube, which measures relative air speed.
