Stupid People Refuting MythBusters over Plane/Conveyor Belt
Posted January 31st, 2008 @ 11:13am by Erik J. Barzeski
The (in)famous "Plane on a Conveyor Belt" experiment was run last night on MythBusters and, as physics dictates, the plane takes off.
That was a terrible experiment. The whole basis for the myth was that the airplane could take off from a treadmill traveling at the same speed as the aircraft. Unfortunetly during their testing they failed to keep the aircraft and the treadmill at the same speed. It is clearly evident from the video that the aircraft is accelerating faster than the treadmill is being pulled. If they were moving at the same speed the aircraft would not be passing all the cones while on the treadmill...it would remain in a stationary position relative to the cones.
The physics are totally wrong, an aircraft doesn't fly because of a propeller, ie a glider. It flys because of the air flow over the wings creating lift. If you were to run 20 mph down a road your hair would blow in the wind stream being created. If you run 20 mph on a treadmill your hair will look just as pretty as when your standing in place. Its the same principle with a wing.
The myth is a scam. They need to retry the myth with a pilot that can keep the plane at the same speed as the treadmill.
- It's not clearly evident.
- The aircraft would still pass all the cones (just as it would if it were on ice). It most definitely would not remain stationary.
- The physics are correct. Lift is generated by airspeed. Forward motion is generated because the engine (jet or propeller) acts against the air, not the ground.
- A person running has nothing to do with it. That's the "car" problem. Strap a jet pack on a person running on a treadmill and you've got the equivalent version.
Why can't these idiots get it through their thick skulls that the plane moves relative to the ground? They seem to be basing all of their opinions on the assumption that the plane stays still due to, I dunno, magic??? Even the most basic version MythBusters ran - the actual plane on the treadmill - proves them otherwise. The propeller pulls the plane through the air.
The only shocking thing to me in the entire episode was that 400 pound planes exist and they can take off going only 25 MPH!!!
More quotes below, because, well, why not? It's like spectating a car accident. In the voice of Haley Joel Osment: "I see stupid people."
Please note: all the quotes below are incredibly stupid and WRONG. I've left the names off to protect the stupid, but they can all be found at the MythBusters forum link above.
I think they blew this one. The whole object of the conveyor belt was to keep the plane from moving. The plane still moved. Thus not busted.
I think they would have better luck tying the plane with a long rope to keep it from gaining forward motion while still allowing it to gain upward motion and trying that instead of a treadmill.
They needed to account for the forward motion of the plane. They did not measure how far it took the plane to take off while on the conveyor belt. I'm betting it was the same distance as off the belt.
Excuse me, but as the videotape proves, the planes (both scale and lifesized) were moving. As the tape clearly shows, the plane was NOT traveling at the same speed of the treadmill, as the plane was moving FORWARD in relation to the pylons that were on either side of the runway. Therefore, air WAS moving under the wings by the action of the movement, NOT THE PROPELLOR.
Do you REALLY think that the NAVY would spend BILLIONS of dollars on catapult systems for aircraft carriers, if they could have just gotten away with having a treadmill instead.
GET WITH THE PROGRAM PEOPLE. It is all physics, just like the pilot Mark said: If I move the air provides lift, if the treadmil matches my speed, then the plane will be a brick.
This has NOT been proven at all.
Presuming the 'conveyor belt' was moving at 25 mph and the plane was not powered, it would be moving backwards at 25 mph. When the prop turns sufficiently to pull the plane forward (without the tarp) at 25 mph it will have lift off, but when on the tarp, the forward speed is cancelled by the reverse speed of the 'conveyor belt'. Therefore the plane moving forward at 25 mph means the engine is revving sufficient to overcome the tarp plus 25 mph (total 50 mph) and creating lift off at its required forward speed.
The plane and the conveyor belt were NOT traveling at the same speed. If they were, the plane would be stationary. It wasnt hard to see the plane was moving forward pretty fast, obviously faster than the belt. So its ground speed was still fast enough to reach takeoff speed to produce enough lift on the wings to fly. The prop doesnt make the plane fly, the wings do. Shut an engine down during flight, what happens, you glide. Cut your wings off in flight, see what happens.
I have lost all faith in humanity. I am truly disappointed in the MythBusters on this one. This myth should never have made it past the so-called "science content" segment. A plane is able to fly because air is passing over and under the wings at a certain velocity. This myth is a question of relativity. If the plane and the conveyor belt are moving at the same speed but in different directions, the plane is still NOT moving relative to the air. The ultralight plane in the episode took off because it was moving fast enough relative to the air to create lift under the wings. The conveyor belt was not moving fast enough to keep the plane stationary relative to the air. If you can't understand this concept, I would suggest opening a physics or calculus III book. Books can usually be found in libraries. If you cannot find a library, try google searching "how a plane flies."
Is this the only way to make a formal critique of the method used to test this myth? I just want to make a point in the hopes of clarifying a few things.
First, if you watch the footage from the show you can see that the plane is moving relative to the cones on the ground which, i assume, are stationary. Therefore, the plane is moving relative the ground and the basic premise behind the myth (that the plane is not moving relative to the ground because it is traveling on the belt of the treadmill at the same speed that the belt is moving in the opposite direction) is not what is going on in the experiment. To test the myth properly, the plane must remain stationary relative to the ground.
Second, the speed of the truck pulling the treadmill being higher than the take-off speed of the plane means nothing. The take-off speed is the speed relative to the ground required to give the plane enough lift to take off. The plane's wheels could make it travel much faster than that if the plane would stay on the ground. The treadmill just increases the speed the wheels have to go to get the plane to the take-off speed relative to the ground.
The episode proved that a plane can take off with a 25 MPH tail wind. It did not prove that iit could take off if it was standing still in relationship to the ground/air.
The proper test for what they were trying to prove is almost as simple as what they did, but requires a bit more preflight testing.
What they need to determine is the propellor speed at which the plane will reach 25 MPH. (It will work because this is a fixed pitch prop)
Get the truck/tarp moving at 25 MPH and increase the airplane's throttle until the proper RPM is reached, if the plane does not take off, keep increasing the throttle until it does.
If it requires 20% or more rpm then I would say that a plane cannot take off on a conveyor belt that continues to increase its speed porportionately to the increase in power of the plane.
This guy seems to think the Mythbusters pulled the plane forward with the conveyor belt instead of in reverse:
Wow! I can't believe the Mythbusters folks messed up so bad on this episode. Air has to move over and under the wings to create lift. Newton's Third Law: For every action there is an equal and opposite re-action. There is NO air current (Action A) against the wings to push back (Action B) and create lift. Sorry guys, the truck pulled the airplane forward to create a lift.
This guy is adding words to the problem to justify his misconception. The "wheel" speed is never mentioned in the original problem, and in fact, the wheels go 2x as fast as in a normal, non-conveyor takeoff:
The Myth was, Can a plane take off on a conveyor belt when the "wheels" on the plane are going the same speed as the "conveyor belt" when both are moving the same speed in opposite directions. In that case no it cannot since both will cancel each other out and plane should stay in the same spot on the conveyor belt and the plane will have no forward movement to build airspeed to create lift. In order to the plane to take off, it will need to make up the speed that it needs to take off. So technically the wheels on the plane were going 50mph in that myth and the plane was going 25mph forward to build enough lift under the wings in order to take off. So yes, technically a plane can take off on a conveyor belt but if the conveyor belt and the plane's wheels were going to the same speed, then no it cannot. Myth is still not busted
I'm afraid the only thing they busted was my love for the show. Had they truly matched the speed of the plane (ie 25mph) to the belt and not have throttled the engine (thus prop) to more than a 25 mph pull it would have never took off. What a shame they didn't realize this in time to do a decent show.
I would just like to point out that, if in fact, the plane was indeed going as fast as the "treadmill" tarp pulled by the truck, there would be no forward motion. The plane has forward motion and is indeed going faster than the tarp is being pulled. Therefore, the plane is able to get air under its wings and thus has the ability to generate lift. When you understand that air speed generates lift than you can see that if in fact the plane and the treadmill were going at the exact same speed, there would be no forward motion, momentum or wind speed generated by the plane moving. It would be as if the plane were static, that is if they were the same speed (the "treadmill" and the plane) then the plane would have no lift generated by movement. Hence it would technically not be moving. It is impossible to lift if the plane has no forward mmotion. I know this is excruciating detail but it just not possible if the plane was static like the car in the episode. It only took off because it was going faster than the tarp. Point blank. If you watch the episode, the plane moves past the cones which would be impossible if both the plane and the tarp were going the same speed.
Ok I'm new, But it seems most of the later posts got it correct.
The aircraft moved past the trafic cones (it had ground speed), the wing had lift.
Had the aircraft not had foward movement, but relied only on engine thrust (coveyor and aircraft speed REALLY match); (provided thrust made enough lift over the wing). The aircraft would lift vertically before it would move foward.
An airplane's propeller pulls the plane through the air, causing lower pressure on top of the wing than under it*, which is what lifts the plane.
The propeller does not push enough air across the wing surface to cause a great enough pressure differential for the plane to overcome gravity.
If the full-size test were actually done precisely, the plane would have stood still with respect to the ground.
Instead, the plane accelerated down the runway, passing cones all the way.
The same is true of the small-scale test: if the speeds were exactly the same, the plane would have remained still with respect to both the ground and the frame of the treadmill.
If the "forward motion" of the plane exactly equaled the "backward motion" of the treadmill, there would be a net-zero wind passing over the wings, and therefore no lift. This should be true even if moved at double or triple the minimum takeoff speed because you still have a net result of no wind over the wings. Less physical strain on the hardware, but really no different than mounting the plane on a pole - the plane can not move forward through the air, therefore it can not generate any lift.
Let me try to explain this slowly: If the aircraft does not appear stationary then the speeds are not matched.
Let me try to explain it slowly: If the aircraft is stationary, it has no speed TO match.
This was a huge oversight! The ground camera clearly showed that the plane had forward motion. Anyone that knows anything about how a plane flies knows that the wings must have air flowing over them in order to produce lift. Spinning the wheels does nothing to produce lift. The experiment proved nothing. I don't know why the pilot didn't contest the validity of the test!
The plane moved forward. It was beyond the cones when it took off. The plane was accelerating faster than the treadmill was moving...thus it had airflow over the wings, which provided the lift for take-off. Most aircraft cannot accelerate straight up...they need airflow over the wings to to produce "lift". Only a few, mostly military and acrobatic aircraft...and most R/C models...can accelerate vertically...which means the thrust is overcoming the weight. Do this "busted" myth again with a camera placed 90 degrees from the plane. Keep the plane in that position and pull the conveyor belt as fast as you want...the plane won't take off. The propeller won't produce enough airflow over the wings to produce lift.
I'm a pilot, I'm solidly in the no fly group. In fact it is hard to believe there is a "fly" group. Then mythbusters says "busted". Puhleeze... All this myth proved is that the airplane( in both cases) has more than enough thrust to fly faster than its take off speed (11 and 25 MPH). In fact the yellow plane probably can fly at 80 mph. So unless the conveyor also sped up to 80 the plabne would generate lift and fly. To prove this myth the planes must be limited to ONLY their minimum take off power and speed. This can be verified by manifold pressure and tire speed. At any time that the power exceeds the minimum, clearly the plane is going to start to go forward (shown initially as tire speed increasing). If the plane is allowed to accellerate it is clearly going to generate a bit of lift. At this point the wheels will no longer be in firm contact with the conveyor, the (relative) conveyor speed will diminish (as shown by decreasing wheel speed) The (relative) aircraft speed will increase by this corresponding amount and the aircraft will IMMEDIATELY fly. Basically as soon as either plane moves forward in the frame and generates a bit of lift, then the myth is over as the conveyor and planes are no longer moving at the same speed.
There should have been a science content here, but then there would have been no show. To call it busted is just a way to generate letters and NO ONE could be that stupid.
I love the people who say "it was not supposed to move because moves at the same speed." Do they not see the blatant disregard for simple logic?
Just because you saw it on television doesn't make it true! Granted the mythbusters are pretty awesome but they're not perfect. And in this case, boy were they wrong. Anyone who has taken a physics class knows that a plane needs air passing over and under it's wings to take off. And in order for the air to pass under/over the wings it has to be moving. From what the mythbusters said the plane was not supposed to move because it was moving at the same speed that the conveyer belt was moving but in the opposite direction. I really think they need to revisit this myth or at least explain what happened and why their "busted" really wasn't.
I agree with all those who say that this myth needs to be redone. The plane and the conveyor belt weren't going the same speeds, if they were, the plane would have stayed stationary. They show the speed of the ultra-light on the practice run, but don't show it during the test and they never show the speed of the truck Jamie is driving. As a pilot (and I hope all other pilots know), you need airflow over the wings to make an airplane fly. A stationary plane with no wind will not create any lift so the plane will not fly. The plane in this myth was moving down the conveyor belt so it was able to create lift by flying faster than the conveyor belt and was able to take-off. If the idea of this myth was just to see if a plane could take-off from a conveyor belt, then yes it is busted, because all you have to do is get the planes speed up to conveyor belt speed plus take-off speed and the plane will take off. But if the myth is that a plane can take-off while matching the conveyor belt speed, this myth is far from being busted. If they decide to redo this myth, I don't see why they can't build an actual conveyor belt to place the plane on. According to the show, they were using an ultra-light aircraft that only weighed 300 lbs, are you telling me that after all the experiments that they've done, they can't build something like that. It would be able to show exactly how fast the belt is actually moving.
This guy talks (correctly) about a small issue with the host's explanation: the engine (and propeller) pulls the plane through the air, it doesn't blow air over the wings.
I think the guys got it right on the show. The plane should take off from the conveyor. However, their explanation of the physics was completely wrong. The plane does not take off because of the propeller moving air over the wings. The plane takes off because the propeller pulls the plane through the air, this movement of air over the entire wing allows the plane to fly. If the propeller were enough to keep the plane aloft, then why are the wings so large? By this theory you would only have to have enough wing directly behind the propeller. This can also be proven by testing with a "pusher" style aircraft, one with the propeller behind the wing. It would also take off with this test. To further clarify this whole thing, they should have been measuring air velocity at the wings, not ground speed at the wheels.
Donate Life
Posted 31 Jan 2008 at 1:02pm #
And by calling these people "stupid" and "idiots" you achieve what exactly?
Posted 31 Jan 2008 at 1:19pm #
Any pilot in the "no fly" camp is no pilot that I'd want flying the plane I'm in....
Posted 31 Jan 2008 at 1:23pm #
Carl said on January 31, 2008:
I succeed in telling the truth? In calling a spade a spade? What would you have me call them? The word "stupid" and "idiots" mean something, and to me, the definitions pretty much line right up with what these people are doing, saying, typing, etc.
No doubt I could have used synonyms, but then you'd just be asking me what I achieve by calling people clueless, dolt-like, unintelligent, braindead, deficient, dim, dopy, dumb, foolish, mindless, moronic, obtuse, thickheaded, unthinking, slow, ignorant buffoons.
bbum said on January 31, 2008:
Indeed. I'm amazed at how many of the "no fly" people are outing themselves as pilots. Wow.
Posted 17 Dec 2011 at 6:57pm #
If you wantr to call a spade a spade then you should be pointing out that the people in the no-fly camp probably have IQs below 130. I can imagine that someone with an IQ in the 120s might fall into the no-fly camp. So these people are not necessarily stupid, but they are not gifted.
Posted 31 Jan 2008 at 7:34pm #
Maybe a good way to refute this for the nonbelievers would be with a seaplane. No wheels, just skids.
Seaplanes, obviously, can take off just fine facing upstream up a river no matter how fast the water is going. Might help them visualize how the treadmill just doesn't matter.
Posted 31 Jan 2008 at 9:34pm #
Carl said on January 31, 2008:
he made me laugh while pointing out some really obvious points that all these people would have understood if they were just more intelligent.
Posted 15 Feb 2008 at 7:45pm #
An airplane with mass M sits on a conveyor belt. The airplane's jet engine is turned OFF. The conveyor belt starts moving backward at a constant velocity V_conveyor. (note that all velocities will be quoted relative to the ground referential)
Which direction does the plane go? Backward, with velocity V_conveyor.
Intuitively it is reasonable to expect that the plane will have to overcome this backward velocity before taking off.
At time T=0, the jet engine is turned on, generating a thrust, F by pressing against (we all agree) the atmosphere. As a result, the plane experiences a forward acceleration A = F/M. Note that the conveyor belt provides no acceleration, just constant velocity. [As an aside, also note that acceleration is independent of any fixed frame of reference].
We are allowed to decompose the velocity of the plane relative to ground (V_total) into the velocity component due to the conveyor belt (V_conveyor) and the velocity resulting from thrust acceleration (V_plane):
V_total = V_plane - V_conveyor
As velocity is the integral of acceleration, at the instant in time T=0 its (forward) velocity component due to the thrust force is still V_plane = 0: the plane is still moving backward relative to earth with velocity V_conveyor - V_plane = V_conveyor.
Time, T, continues to pass. Thrust F guarantees constant acceleration A=F/M, and the equation for the velocity of the plane due to thrust is V_plane=TA.
Thus V_total = TA - V_conveyor. The plane's ground speed V_total will be zero only when
T_null = V_conveyor/A
Until this time the plane will continue to move backward. As more time passes, the plane's forward velocity component due to thrust will continue to increase linearly with time, whereas the backward velocity component due to the conveyor belt motion will remain constant, and so the plane will progressively pick up forward velocity (V_total = TA - V_conveyor > 0 ), develop lift and take off.
Thus if the conveyor belt has constant velocity the plane will, of course, teventually take off. If the conveyor belt's velocity increases linearly with time at a rate A, then the plane will not develop forward velocity and will not take off.
Posted 17 Dec 2011 at 4:00pm #
Tom. You are correct in everything you say until the last paragraph. As soon as the plane's engines overcome the friction between the wheels and the treadmill the two systems (plane and treadmill) become independent. This means that the treadmill's action no longer is communicated to the body of the plane. This means that the treadmill can be accelerating (not constant velocity) and the plane will still take off.
Posted 15 Feb 2008 at 8:16pm #
Tom said on February 15, 2008:
No. If the brakes aren't on, it's quite possible that the conveyor belt could be moving backwards faster than the plane. Put a roller skate on a tablecloth and yank the tablecloth. Unless you gradually accelerate so as not to overwhelm the resting friction, the skate doesn't immediately move at the same speed as the tablecloth.
And that's without the roller skate supplying its own force opposite the direction of the table cloth (as we have with the plane).
Your math is wrong, your physics are wrong, and your methods are incorrect. V_conveyor accounts for almost no impact on the plane's velocity because the conveyor belt applies almost no force horizontally. The only force it applies is UPWARDS, to counter the weight of the plane. The "backwards" force it applies (opposite the forward direction of the plane) is supplied by the ball bearings and is, again, negligible.
You are wrong… and it's funny you'd come to a post making fun of people who get it wrong and then do as you did.
Posted 15 Feb 2008 at 8:27pm #
Erik,
This is not a frictionless world. If you wear rollerblades and setp onto a conveyor belt you may indeed not *initially* move with the conveyor belt but in a few short moments you will have the same velocity as the conveyor belt. The quality of your ball bearings has nothing much to do with it in the long run.
In other words once equilibrium is reached you will be moving at the same speed as the conveyor belt.
Once that occurs, when you turn on your jetpack the wheels and their bearings are essentially immaterial and the rest of the calculation holds.
Posted 15 Feb 2008 at 11:09pm #
Tom,
Your claim is that the rolling resistance of the ball bearings will be great enough to stop the plane from moving forward relative-to-the-air to the point of achieving lift off.
Given that claim, which is actually subtly different than the original claim, then it becomes a question of how much thrust can the plane's engine provide vs. how much rolling resistance can the wheel's bearings provide.
In general and without the bearings failing catastrophically, the answer is "a lot of thrust" vs. "very little resistance".
The quality of the bearings very much do matter simply in that your scenario would require the conveyor belt to be going at 100s or 1000s of miles per hour to provide enough rolling resistance to counteract the thrust of its engine.
Sure -- when you modify the original claim as you have, it could theoretically be possible to pull the conveyor belt "backwards" fast enough to create enough rolling resistance to prevent the plane from taking off.
More likely, at the speeds involved, the bearings would fail catastrophically and this would become a considerably more sparky experiment.
Given a powerful enough engine, the presence/absence of rolling wheels is irrelevant. It becomes entirely a question of whether or not you can achieve liftoff prior to the wheels, struts, and belly of the plane being worn through.
b.bum
Posted 16 Feb 2008 at 4:41am #
B.Bum,
I actually made no claims about bearing resistance; I'm just giving an example of one of the possible limits of the problem (plane has initial backwards velocity) and how this allows you to start thinking about the problem in simple terms that can then be built upon (first, initial velocity and momentum; only afterwards should you to start build up your model by considering friction).
Solving physics problems is all about stating your initial hypotheses.
1. If the wheels have zero friction, then the conveyor belt is a red herring because its motion will not be transmitted to the plane, ever. The plane having the advantage of acceleration will always take off.
2. If the wheels have infinite friction, then the plane won't be able to roll forward and will always have the same velocity as the conveyor belt. The plane will never accelerate and never take off.
Clearly, the real world is in between. So "solving" the riddle is a question of how your assumptions balance out. Although this was not my initial guess, I do agree that in the real world no conveyor belt would succeed in transferring its full acceleration to the plane, and that the plane will always take off.
Just to beat a dead horse:
IF the conveyor belt has constant velocity -- as was the case in the Mythbusters show -- then the plane will ALWAYS take off under ANY additional assumption (see above)
IF the conveyor belt is accelerating, things get tricky and indeed you have to get into issues of static friction etc. etc.
Posted 16 Feb 2008 at 9:49am #
Tom, no further comments from you are necessary here. Please move on.
Tom said on February 16, 2008:
No, you're not. We've been given a set of rules, either "reality" or the ones given in the stated problem. We're not interested in making up new versions just so that, under an unrealistic set of expectations, the conveyor belt has very much impact at all on the plane's forward progress.
The acceleration or not is a moot point, and if you think an accelerating conveyor belt somehow changes the rolling resistance, you're wrong on that count as well. Friction remains largely the same once the wheels start rolling, and by "same" I also mean "next to nothing" - nil, negligible.
Tom said on February 16, 2008:
The wheel friction is so close to zero, that this is indeed how people grounded in reality choose to look at the problem.
Tom said on February 16, 2008:
Actually, you'd have to lock the plane to the conveyor belt for this to be true. Otherwise I suspect that the plane would simply shred up its tires as it drug them over the pavement. Sea planes can still take off from water, after all - and they don't have wheels. So again, you're wrong.
Tom said on February 16, 2008:
Yet in either case, the plane takes off. In the second case - the wildly unrealistic one - it's admittedly more difficult (and the wheels may shred and blow up, and sparks may fly as bbum said), but it still takes off if it's not literally locked to the ground.
Tom said on February 16, 2008:
No, they really don't get tricky at all. Acceleration's impact on the rolling resistance of ball bearings is minimal/negligible.
Really, no further comments (from anyone on either side) are necessary.
Posted 08 Dec 2008 at 8:57pm #
I think maybe the easiest way of thing about this is to consider the wheels to be like ice skates. Would a plane on big ice skates in a skating rink have trouble taking off? No. It wouldn't. Because the propeller pulls the plane through the air. No friction with the ground is necessary to move the plane.
Now consider if the ice were magically moving underneith the plane, would it cause the plane to move? No, it wouldn't, because ideally there is zero friction between skates and ice.
Since there's no friction, the movement of ice underneith plane does not change the plane's force in any significant way. Therefore when the propeller is turned on and the plane gets force forward, it will move forward and take off just like normal.
Magically moving Ice / skates, and Conveyer belt / Wheels and analoguous. It's the exact same situation.
The fact that the plane takes off just like normal, regardless of if the ground is moving underneith of it, is what busts the myth. That is exactly what the pilot commented about when he got out of the cockpit. He said "it took off just like normal!", meaning he didnt' have to gun the engine further to "outrun" the conveyer belt.
Oh well. This whole thread has been pretty amusing
Posted 09 Dec 2008 at 2:19am #
Yeah, except if you look at the video the "conveyor belt" is replaced by a thin plastic tarp. Do you honestly believe there is "zero friction" between the wheels of the plane and the immobile ground beneath the tarp?
Posted 09 Dec 2008 at 7:09am #
Tom said on December 9, 2008:
Tom, after all of the above do you really want to look this stupid?
Posted 09 Dec 2008 at 7:25am #
Listen dude, I don't know why you get off insulting people but I'm sure it helps you feel superior, and if so then great for you. I have a PhD in experimental physics and have published papers in eminent physics journals, and I've discussed this problem with OTHER researchers who have PhDs in physics -- and guess what ? The answer they give is 50-50, so its not as trivial as you may think it is, I don't care what you say or think, and frankly I'm not afraid to "look this stupid" once in a while as I am not that insecure. If it were that trivial a problem would a TV show have spent money to try to prove or disprove it?! Would hundreds of people argue about it if it were that trivial? If you can't enjoy toying with a problem or the limits it pushes then that's your issue, and if you can't discuss things with people without insulting them than I simply feel sorry for you, for all of a fraction of a nanosecond. But I guess that's why you have a blog, to feel superior and allmight. And as I said that lame plastic tarp does not do justice to the problem as it is laid out.
Posted 22 Oct 2010 at 11:02pm #
Tom, did you receive this PhD in "experimental" physics online? at what university did you study? If you're not afraid to look stupid, please link us to some of your publications... oh wait, you can't? hmmm...
It's shocking that with so much effort put into this people still cannot grasp a relatively simple concept, and may even try to use some phony-bologna physics.
Posted 09 Dec 2008 at 7:57am #
Tom said on December 9, 2008:
Let's be clear: I don't "get off" insulting people. I get off insulting incredibly stupid people. If you're even remotely as educated as you claim, then I'm ashamed for you, the schools you attended, and your friends.
Tom said on December 9, 2008:
Have you watched Mythbusters? They don't exactly limit themselves to the most complex of issues. "Can you wrap yourself around a swingset?" "Can you escape from sand when buried up to your neck?" "Will Mentos and Coke explode?" are a few of their "myths" and I'm certain there are sillier ones than those.
Tom said on December 9, 2008:
People argue about it because they think the thrust comes from the wheels. Once they realize that, no, the wheels are just there to spin, they get over it. Millions of people argue about it because it's a brain teaser that requires a shift in the way we normally think about propulsion.
Tom said on December 9, 2008:
Ooh, did you learn about nanoseconds while you were getting your Ph.D? This question pushes no limits. If it pushes yours, again, I feel sorry for the "degrees by mail" college from which you claim to have received your degree.
You've obviously subscribed to the comments here, which is why you post so quickly after someone else does. I've taken the liberty of removing you from the subscription list. As I said before, no further comments from you are necessary here. Move along.
Posted 14 Dec 2008 at 4:15pm #
Free body diagram. Force from the engines pushes the plane forward through the air, mass*gravity and the normal force cancel each other, and the wheels provide a negligible resistance to motion in the opposite direction.
end result. Plane is pushed forward, air moves over the wings, and the plane takes off. Erik is right
PLEASE NO MORE FAKE PHYSICS!
kthxbai
Posted 20 Dec 2008 at 11:39pm #
Just watched a rerun of this infamous episode and had to sound off. I am not an engineer or a pilot but its a pretty simple concept to me. Rather than reiterate the logical arguments already noted here lets propose some thought provoking comments and questions for those who don't seem to understand:
1. If you believe the wheels have any real impact on take off, what happens after flight is achieved?
2. The conveyor belt is basically only spinning the wheels faster. Thats all it is doing..
3. We have not unearthed some new way to decrease the size of runways because of this, it actually shows the plane takes off at around the same distance as it normally would (because the wheels have almost no impact on propulsion). Not because of any conspiracy or discrepancy in matching the opposing speeds.
4. Go ahead and increase the speed of the conveyor, see what happens.
Posted 22 Jan 2009 at 6:06pm #
I think the problem is that everyone interprets this problem differently.
When we are talking about the plane going the same speed as the treadmill, some people think of that as relative to the treadmill, and others think of it as relative to the ground.
If you think of it as relative to the treadmill, then you are visualizing the plane being stationary on the runway. If this is the case, then then the plane will NOT TAKE OFF.
If you think of it as relative to the ground, then you are thinking about the opposite case where the plan is providing normal forward thrust. In this case, the plane will move forward at near its normal speed, and will TAKE OFF NORMALLY.
I've never suceeded in finding the original wording of the question, but I really think everyone should stop bashing everyone else just because they have a different opinion. We've started a few too many wars that way.
Posted 22 Jan 2009 at 6:33pm #
Eric said on January 22, 2009:
With all due respect, no. Since the treadmill is moving opposite the direction of the plane, the plane-to-treadmill speed will always be twice the plane-to-ground speed. There's no way for the treadmill to "match" the speed of the plane (relative to the treadmill) unless the plane's speed is 0 (in both frames of reference).
The only logical frame of reference for the plane's speed is plane-to-ground. You can't have a plane-to-treadmill speed measurement that affects the speed of the treadmill.
Posted 19 Feb 2009 at 4:37am #
Anyone wanna check my physics on this?
The instrument inside the pickup truck is a speedometer, which measures miles per hour away from a fixed point. (I know, I know...speedometers are linked to the wheels of the truck to get that measurement, unless it's a GPS based speedo, but just go with me for a minute, mmmkay?)
Now, imagine there's an instrument in the plane that's an air speed indicator. It isn't linked to the plane's wheels nor to GPS, it measures air movement through a tube mounted somewhere on the plane, and expresses the plane's speed relative to teh air around it. (I know, it's crazy, but just give me a minute, okay?) Just for simplicity's sake, let's say this instrument is also marked with "miles per hour."
That plane is going to lift off the ground when its airspeed hits 25 mph. If it was sitting still, engine off, facing into a 25 mile per hour wind, the plane would lift off the ground, right? (Yeah, someone would have to hold the tail up, in order to get the proper angle of the wings so that lift was created, and the pilot would have to monkey with flaps and such, but go with me. Yeah, I know, the plane would lift very slightly, then quite probably tumble backward, pretty much ruining the day of the guy holding up the tail....)
Conversely, if there was a 25 mph wind blowing, would the plane take off running downwind? No, not until it went 50 mph, measured from a fixed point on the ground.
I guess my point is that the treadmill is moot. My physics professor, Sister Bertrille, said, "When lift plus thrust is greater than load plus drag, anything will fly." She never got around to explaining how to hover, and she was so darn cute when she said "thrust." She never mentioned a treadmill.
What? Oh, yeah. There are four frames of reference here. Treadmill speed relative to the ground, plane speed relative to the ground, plane speed relative to the treadmill, and plane speed relative to the air. Guess what? The first three are moot. The last one is the only one that will produce lift and/or flight.
On the TV show, the model plane shot forward, off the treadmill. The full-scale plane shot forward past the cones before its wheels lost contact with the tarp. But it didn't really matter how fast the plane was moving past the cones....it only mattered that the plane had 25 mph worth of air speed. If there was a headwind that gradually increased to 25 mph, as the pilot increased engine speed to keep the plane lined up with one of the cones...viola, the plane would have lifted off the ground, and appeared to hover.....(virtually) regardless of tarp speed or truck speed.
One final thought. The plane didn't fly because it reached a ground speed of speed of 25 mph. It flew because it reached an airspeed of at least 25 mph, at which point its wings generated lift and it's engine generated forward movement. If all it took to fly was ground speed, we wouldn't even need the plane; all we'd need is a 400 pound pickup truck, right? And all we can simulate with a treadmill is ground speed, right?
And anyone who disagrees is a doodyhead, and went to a doodyhead school.
Posted 30 Mar 2009 at 11:31am #
A = wheel speed
B = Conveyor belt speed
C = speed due to plane's Thrust
Stationary
A = B (0 = 0)
Moving
If the vehicle was propelled via the wheels then…
A = B (5 = 5)
If the vehicle was propelled via an outside force then….
A = B + C
if C is 0 then A = B
If C is any other value than 0 then A and B are both infinate.
So either the question is broken as any forward thrust breaks the simple equation OR as soon as the plane starts accelerating the wheels and treadmill will accelerate to infinity regardless of the speed of the plane as long as the plane is moving.
If the plane is stationary then the treadmill is stationary
if the plane moves then the conveyor belt and wheels will be travelling at an infinate speed.
Posted 30 Mar 2009 at 11:46am #
Dale said on March 30, 2009:
No. The conveyor belt doesn't match the wheel speed - it matches the plane's speed relative to the ground.
Posted 07 Dec 2011 at 6:20pm #
And that is why the broadcast is a hoax, because the conveyor doesn't match the wheel speed. A properly conducted experiment would match the conveyor speed to the wheel speed, and the plane wouldn't take off.
Eric, you childish, cowardly, name-calling quivering pitiful specimen - go throttle up to full the propeller of a plane with it's wheels chocked (the analog to the velocity-matched conveyor) and wait for the plane to take off. Then see what hapens first - the plane taking off, or your fear/hatred/ineptitude becoming illuminated to you.
Posted 08 Dec 2011 at 8:46am #
mlandersmd said on December 7, 2011:
Hey moron: they never said wheel speed. Since the plane is moving forward the wheel speed will always be 2x the belt speed (if you're measuring on the outside of the wheel) except when both are 0.
Of course, if you measure the speed of the wheels as the center point of the axle, then the speeds did indeed match up.
People claiming the experiment was conducted in a a "wrong" way are simply trying to account for their stupid misunderstandings.
Posted 13 May 2009 at 2:54pm #
The main problem with the "no-fly" people is that they are assuming that matching the plane's speed with the treadmill means that the planes ends up not moving.
A. This is impossible, because if the plane is not moving horizontally, but the treadmill IS moving, then you have already violated the terms of the problem. Let me use a 747 as an example. The take-off speed is 180mph. People who say that if you put a plane moving forward at 180mph on a treadmill moving backwards at 180mph, the plane will not move. Well, if the plane isn't moving, then there's no speed to match. So then to keep the terms of the problem in line, the treadmill must stop.
B. Any reasonable person would agree that the reason we have wheels on plane is decrease friction against the ground as much as possible. So you have very little friction against a stationary ground while the plane propels itself through the air (guided along the horizontal plane by the ground) until it builds up sufficient speed to lift off. So why would introducing a treadmill into the equation suddenly produce enough friction to keep the plane from moving? There is SOME, but very little, friction against the ground when the plane takes off. Let's say ground friction is F*1, which obviously doesn't hinder the plane in any way. If you put the plane on a treadmill going in the opposite direction at a proportional speed, then all you get is F*2, meaning the treadmill is moving backward relative to the plane at twice the speed of a normal runway. How would that stop the plane with the massive amount of thrust it produces?
Posted 22 Jun 2009 at 6:44pm #
Lets keep this simple. A paper airplane does not need much lift to "fly" (glide). Therefore, if you're running on a tread mill with a paper airplane in hand, and just let go of the airplane, will it fly ahead of you? No, it will drop to the ground. Why? Because while there may be enough theoretical forward motion (ie: your running) for it to fly, there is no movement of air over its wings. Even on a treadmill, you are required to toss it forward. Same idea with the airplane on a treadmill. If the airplane matches the movement of the ground below it, without airflow over the wings, there is no lift. Ground speed is meaningless. Its about Airspeed. An airplane on the ground with engine turned off (or a glider) with a Vs of 50 knots will lift off the ground in a direct headwind of slightly over 50kts. Or in other words, an airplane flying at an A/S of 100kts into a headwind of 100kts will have a G/S of 0kts. But its still flying. And thats why some airplanes can fly backwards. If you're flying at 40kts in a 50kts headwind, you're going backwards (relative to the ground).
Put simply, Mythbusters got it wrong. The ultralight was clearly allowed/able to gain forward momentum (faster than the tarp was pulling)(allowing for an airflow over the wings) and therefore, lift. And the RC A/C were allowed to accelerate forwards on the conveyor belts. Jamie getting all "lecturey" about science he clearly did not fully grasp was also uncalled for.
On a side note, if the navy could develop a carrier that could do 150mph, a Super Hornet could lift off the deck vertically.
One day.
Posted 23 Jun 2009 at 7:04pm #
Stu said on June 22, 2009:
It's too bad you left out the critical parts in your attempt to simplify.
Stu said on June 22, 2009:
No, you did.
If you ever do realize why you got it wrong, you're going to feel pretty dumb for a few moments. It's okay. Just let it pass.
Posted 20 Jan 2011 at 7:45pm #
This is the dumbest argument I have ever heard. Holding a paper airplane while running in a conveyor belt and then just letting it go = equivalent to a plane with propeller or jets on conveyor belt? DUH.
You still can't get your head around that the wheels on an airplane are FREE SPINNING and have no power. All power is in the propellers or jets. Which acts against the AIR and not the GROUND. You running in a conveyor holding a paper airplane is causing that plane's thrust to be dependent on your legs, which act against the GROUND...you are basically same as a car on conveyor belt which cannot move!
However as you correctly pointed out (but wrongly interpreted), when you push the plane with your arm and let it go, it would still FLY. What you don't get is that the push of your harm on the paper plane is equivalent to the propellers or jets of a real plane pushing against AIR. The action of your arm pushing the plane is INDEPENDENT of the ground. So the paper plane will FLY. And that's why a real plane on a conveyor belt will fly...because the generate thrust NOT VIA WHEELS (which are free spinning like the wheels on a skateboard), but via the propellers or jets, which push on air, independent of what is going on in the ground.
All the conveyor belt does is make the wheels spin faster!
Posted 23 Jun 2009 at 7:27pm #
...sigh...
I don't think either opinion is dumb or even wrong for that matter. There are two very different questions being proposed.
Lets start with this. Put the plane on the treadmill, leave the engine off, and start the treadmill. What will happen? The plane will start to (VERY SLOWLY) move backwards, but the wheels will begin spinning FORWARDS. Can the plane take off? No. There is nothing pulling it forwards. Note however, that the plane has not gone shooting backwards, because of the wheels.
Now start the engine, there are two throttle levels we want to look at, which correspond to the two different schools of thought.
Throttle 1:
At a very, very, very low propellor speed (not one that a plane could ever take off with), the plane will stop moving backwards, and will hold still on the treadmill. The wheels will begin to spin at exactly the same speed as the treadmill. The plane will NOT take off.
Throttle 2:
If the pilot pushes the thottle up to takeoff speed, the plane will begin to move forwards, and will eventually take off.
Now supposing the treadmill speed was increased too, the plane WILL have to work harder than normal to take off, but for the treamill to actually prevent the plane from moving forward, it would have to travel at a speed that would literally sand the wheels right off the plane. In this case, the plane would probably not take off, and bad things would happen to the pilot.
So the question it comes down to is WHAT SPEED IS THE TREADMILL GOING?
If you think it is going at the plane's normal takeoff speed (say 100 km/h), the plane will certianly take off, and the wheels will just spin a little faster.
If you think the treadmill is going way faster (around 10,000km/h or something crazy like that), the friction in the wheels will hold the plane in place and it cannot take off.
Posted 03 Sep 2009 at 1:50pm #
Okay, so I'm not an avid fan of Mythbusters, nor am I of any kind of scientific accreditation at all...And to be honest, I'm not even sure if they did ANOTHER experiment to amend the problem, but I agree wholeheartedly with Erik. When they did the Segway/Paper model, the radio controlled plane accelerated faster than the paper was being pulled away, but when they interviewed the pilot...I thought FINALLY someone understands the pivotal factor in this experiment! But when the plane clearly accelerated faster than the tarp, and the pilot emerged, absolutely amazed that he was "Wrong" I had to stop my teeth from eating my brain! It was so clear that the plane had advanced forward! (Perhaps even the complete distance it takes for the plane to actually take off on a runway, give or take...) I've always respected the Mythbusters, because as men and women of science and physics, they're always thinking of things my dinky little brain could not. But you didn't need logical thought of any kind to realize that the experiment was flawed. All you needed were eyes. If the experiment HAS been developed again, and aired with a more valid/successful (In the sense of Busted or Plausible) conclusion then I don't think they should even air that episode any longer. With the fallacy being so obvious, I'd be embarrassed as a network to show it over. Sure, there are bumps and bruises in science, that's what makes the scientific method, and the development of theories so forgiving. However, if that theory is to be honored in the scientific community, then you're experiment should be a complete and accurate testing of the hypothesis at hand.
When you think about the experiment as a whole...If they were going to go through all of those resources and funding to test the myth, it was a complete waste if they weren't going to do it properly. I love the show, but in this particular instance, it seemed as if the cast were going to great lengths to prove their belief that the plane in fact could become airborne standing completely still, ignoring in it's entirety the major factor being tested.
I'm just sitting here laughing, because the more I think about it...The more I comprehend that that hour I'm never getting back! What a waste of time it was for me to respect them, and trust them to deliever the truth, rather than to go to all lengths to show their faulty logic could be proven. As a scientist, I think it's important that you can listen to reason, be observant, and overall unbiased about the experiment. I feel as if the logic delivered by the cast themselves was enough to count as a variable! Someone pushing so hard to prove they could...well...prove something!
Posted 03 Sep 2009 at 4:11pm #
the stupid, it burns.
Of course the plane moved forward.
The plane was pushed forward by the propeller.
The wheels in a plane are not powered. They do not move the plane. The wheels just give something for the plane to move upon that is less friction than, say, dragging bare metal around.
Posted 01 Jan 2010 at 5:46pm #
Assuming that there is no wind at the site of the experiment, when the airplane throttle is moved to full, the plane will accelerate and take off. This will happen regardless of how fast your treadmill is making the wheels spin. Of course, if you accelerate the treadmill to 8 gazillion miles per hour, the wheels might fall off making it a bit more difficult for the plane to take off. In that case however, the black hole created by the 8 gazillion mph treadmill will have destroyed the universe and rendered your results slightly irrelevant.
The stupid, it does indeed burn.
Posted 02 Jan 2010 at 7:04am #
When I first watched this episode I admit I thought the challenge involved an aircraft rendered stationary by a moving treadmill, and I thought the experiment was flawed when I saw the plane moving forward. True, I am NOT a pilot, nor do I claim to have a firm grasp on the laws of aerodynamics, but I should not have jumped so quickly into such an erroneous conclusion. I soon realized my mistake when I read the phrase ” A treadmill CANNOT prevent a free-rolling plane from moving forward. The propellers PULL the plane through the air, thus creating lift. The plane WILL take off!”
The analogies of attaching a rope to the back of the aircraft, or holding a toy car stationary with your hand do not apply. THE PLANE WILL MOVE FORWARD AND TAKE OFF! Luckily, I realized my mistake before I posted any letters to the contrary.
I cannot call it a trick question, like the rooster laying an egg on top of a barn, but at first glance it can mislead.
Kind of reminds me of this one…If a space ship traveling at the speed of light turns on its’ headlamps, how fast does the light from the headlamps travel!
Well, maybe not.
Anyway…Naysayers, for a short time I was one of you. YOU ARE INCORRECT !
Posted 03 Jan 2010 at 8:28pm #
I may have been mistaken when I stated in my previous posting that this is not a trick question, like the rooster laying an egg on top of a barn. People HEAR the word “rooster” but ignore its’ implication when they hear the words “lays an egg”. They then set their mind to solving the problem of which side the egg rolls down.
In the question at hand, some people have it fixed in their mind that the “treadmill-airplane” scenario has resulted in an aircraft that is “stationary” in relationship to its’ surroundings. Even though the original myth makes no such determination. It only states that “An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff.”
They ignore the fact that it doesn’t matter whether the surface under the planes’ wheels is moving backwards, forwards or standing still…THE PROPELLERS ON THE PLANE ARE PULLING IT FORWARD AND THE AIRCRAFT WILL TAKE OFF WHEN IT REACHES THE PROPER AIR-SPEED. It doesn’t matter if it’s a toy plane, an ultra-light, a Beechcraft, or Howard Hughes’ Spruce Goose, the result will be the same.
As I was saying, having now overlooked this, they set their minds to the other fact of fixed-wing flight. “Without airflow there can be no lift”. Since they now believe that this plane is “stationary” how can there be airflow? They have reached a correct conclusion, but to an incorrect premise.
I’ve enjoyed myself immensely reading these postings. I hope they continue!
Posted 03 Jan 2010 at 8:29pm #
…but PLEASE stop comparing the airplane to cars, joggers and so on.
Picture this:
A very large airplane is flying 1000 feet above the ground. Beneath it are dangling a number of ropes. Attached to the ropes are an automobile (engine running hard), a jogger (legs pumping),a bicycler (peddling like crazy),a roller skater (well, I guess he’s just hanging there), and lastly, a smaller airplane (propellers spinning).
Let’s cut the ropes, shall we? The car, the jogger, the bicycle, and the roller skater plummet
earthward. The small plane flies off into the sunset.
The others require a surface to maintain motion. The plane is in its’ element. The plane will always move forward even if it never takes off. It will just run off the end of that damned treadmill. It will not stay in place.
I was going to add a surfboard, but that might be a bit much
Posted 06 Jan 2010 at 2:41pm #
It appears to me that the people who are posting on this site and others fall into three catagories.
1) Those who "get it," and understand that there is a major blind spot causing some individuals to arrive at an incorrect conclusion.
2) Those who don’t "get it," and stick to the premise that the plane behaves like an automoble or jogger. That is, will somehow remain in place when the speed of the plane and the treadmill are matched.
3) Those who initially began as category 2s, but later realize they are wrong. These people are most interesting because rather than outwardly "jumping ship" they stick to their original declaration, and try to convice others that there is an underlying "spirit" to the myth that substantiates their claim.
I could argue that there is a 4th group of individuals who belligerently declare that it is a stupid myth and we shouldn't even be discussing it. Evidently, the hundreds of postings we have seen disprove that position. If nothing else, it is an intriguing insight as to how people perceive and go about solving a brain teaser.
All in all, it's great fun. You might want to check out some of the videos on YOUTUBE relating to this myth. I had a few good laughs myself.
Posted 07 Jan 2010 at 8:37am #
I had a gentleman in my place of business yesterday that I happen to overhear tell one of my associates that he had flown his own aircraft down south to visit relatives over the holidays. So naturally I told him the myth.
I was astonished when he replied that the plane would NOT take off! When I asked him why it wouldn't lift off he said "I've studied aeronautical engineering and the plane would need lift to fly" When I asked why there wouldn't be lift under the conditions of the myth he said,"Because a stationary airplane would not have airflow over its' wings". "But I explained that the plane was moving forward at the same speed that the treadmill was moving backward" I replied. "Exactly" he said, "… so it's stationary relative to the ground"
I couldn't believe my ears. It took five more minutes of explanation before I saw the dawn of realization in his eyes. He first tried to say that I had explained it wrong, but finally gave in and sheepishly admitted I was correct.
Who says this topic isn't worthy of discussion?
Posted 09 Jul 2010 at 5:49am #
If there is still someone reading this (or just stumbling about it accidentally as I did) and still thinks the Mythbusters got it wrong, here's a thought.
1. To take off, a plane need lift. This is true.
2. To generate lift, air needs to move past the wings (or airfoil/aerofoil, google it). This is true.
3. The way the plane produces this lift, is by accelerating along the runway. This is true.
4. The way the plane ACCELERATES, (and this is the tricky part) is by applying force by the revolutions of the propeller (which is usuallo also an aerofoil, so technically, it in itself has lift).
To illustrate this, let us change the accelerating force generated by the propeller to something we are all familiar with, say, gravity. We all are familiar with the concept of gravity, yes? Good.
Now, gravity usually doesn't act on the horizontal plane, as we usually experience it. So we shall have to make another change in this thought experiment. Ge shall say that the plane is sitting on a steep, even hill, facing downhill. At this point, we make another abstraction. The wheels of the plane are the only point touching the ground, yes? Hence, the physics of a cylindrical object apply. This way, we can represent the plane with a drum.
Everyone still following for now? We have a drum, on an decline, with gravity applying. Now what happens?
The drum, will, roll. I repeat: The DRUM, WILL ROLL.
Now imagine replacing the hill with a treadmill, at the same angle as the hill previously was. What will happen? The drum will roll. It will revolve faster, yes. But it still has the inclination to go downhill.
This is essentially what happens with a plane on a treadmill. And as the plane has wings (AEROFOILS), as it speeds up, it will gain lift. Hence, it will fly.
Posted 13 Jul 2010 at 1:13am #
Sweet jesus... the explanations justifying Adam and Jaime's conclusions are laughable.
The whole point of the myth is that the velocity and acceleration of the plane are matched by the belt, such that the plane is stationary relative to the ground. Real simple concept.
The fact that the plane - while still on the ground - was moving forward relative to the ground automatically implies that it had greater velocity forward than the belt did backward, thus nullifying the experiment. It doesn't matter whether that forward velocity was generated by the propellers of the tires or the pilot farting last night's chili, or that the plane is a barrel on an incline on ice dangling by a rope in the sky, and whatever other nonsense you goofballs have come up with.
In the Mythbusters experiment, THE CORE PREMISE WAS NOT MET. PERIOD.
Myth not busted. End of discussion.
Posted 13 Jul 2010 at 7:11am #
blockhose said on July 13, 2010:
The whole point was not to keep the plane stationary. Not at all. You're an idiot.
Posted 13 Jul 2010 at 10:16am #
Blockhouse,
At least you are on the correct site "STUPID People Refuting Mythbusters Over Plane/Coveyor Belt"
Nowhere in the test does it state that the plane is rendered stationary in relation to it's surrounding area by the treadmill. THAT is an assumption you, and many others, are making. It is, in fact, a physical impossibility.
Let us all hope that you work in some menial occupation, such as ditch digger or window washer, and not as a scientist, teacher or, God forbid, pilot. Otherwise, the world is in bad shape.
Posted 13 Jul 2010 at 11:12am #
Nowhere in what Blockhouse said is it implied that the plane must be stationary relative to the surroundings.
So speaking of assumptions, let's hope YOU work in some menial occupation and not as a scientist, pilot, or God forbid, an English teacher.
Posted 13 Jul 2010 at 12:58pm #
JCBoston69 said on July 13, 2010:
Uhm, Blockhouse said "such that the plane is stationary relative to the ground." He also said that the movement relative to the ground "nullified" the experiment.
Posted 13 Jul 2010 at 1:26pm #
Oh yes, and you took him out of context...
"The whole point of the myth is that the velocity and acceleration of the plane are matched by the belt, such that the plane is stationary relative to the ground"
This is not what he is expressing is HIS belief. He is saying that the MYTH said that a plane is stationary relative to the ground while on a treadmill moving at the same speed as the plane. If the plane is stationary, then by default the treadmill, matching its speed, must be stationary too.
As he said, not a difficult concept.
The myth, as wrong as it is, is easy to understand. The truth, that the plane would, in fact, take off because it is pushing against air and not against ground is somewhat counter-intuitive to many at first.
Posted 13 Jul 2010 at 1:28pm #
"The whole point of the myth is that the velocity and acceleration of the plane are matched by the belt, such that the plane is stationary relative to the ground. Real simple concept." re: Blockhouse
Thanks, Erik. I was just about to reply. Though perhaps I was a little
brusk with Blockhouse! It just gets frustrating sometimes.
True, Blockhouse didn't use the word "ground", but I use the term "surrounding area" because someone once used the analogy
that the plane and treadmill could be on a boat, or aircraft carrier, or some such nonsense.
If the plane WERE stationary to the ground it would also be stationary to the surrounding area.
Posted 13 Jul 2010 at 1:40pm #
"True, Blockhouse didn't use the word "ground"
Sorry! I meant to write "Blockhouse used the word "ground"
Good thing I'm not a scientist, teacher, or God forbid, a proof reader!
Posted 13 Jul 2010 at 1:40pm #
JCBoston69 said on July 13, 2010:
The myth never said the plane was stationary relative to anything.
The myth said that the belt matched the "speed" of the plane. Whether you're measuring air speed or ground speed (they're the same when there's no head- or tail-wind), the belt moving left at 20 MPH does nothing to affect the plane moving right at 20 MPH - relative to both the GROUND and the AIR.
Posted 13 Jul 2010 at 2:18pm #
"the belt moving left at 20 MPH does nothing to affect the plane moving right at 20 MPH - relative to both the GROUND and the AIR."
I know this to be true. The myth, as I recall, is that a conveyor belt matching the plane's speed in the opposite direction would prevent the plane from taking off. if the plane's speed is being measured relative to the belt, then it can never actually match the plane's speed.
Proponents of the myth are stating that the plane would be stationary if the belt matched its speed...which cannot be the case because then the belt would be moving and the plane would not (even though this is not possible unless the method of propulsion is through the wheels of the plane), meaning that the belt is no longer matching the stationary speed of the plane.
Posted 13 Jul 2010 at 1:58pm #
You are completely correct, JC, and I understand perfectly what Blockhouse believes the myth is implying. What I, and many others are saying, is that the myth makes no such implication. It does not say that "a plane is stationary to the ground while on a treadmill moving at the same speed as the plane." Your words.
An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff.
The above sentence is taken from the MythBuster web site relating to this topic. All I am saying is that this assumption, that the plane is stationary to the ground, is what is blocks them from seeing what is actually happening here.
I agree that it is counter-intuitive. That's what makes it so much fun!
Posted 13 Jul 2010 at 2:18pm #
You are completely correct, JC, and I understand perfectly what Blockhouse believes the myth is implying. What I, and many others are saying, is that the myth makes no such implication. It does not say that "a plane is stationary to the ground while on a treadmill moving at the same speed as the plane." Your words.
"An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff."
The above sentence is taken from the MythBuster web site relating to this topic. All I am saying is that this assumption, that the plane is stationary to the ground, is what blocks them from seeing what is actually happening here.
I agree that it is counter-intuitive. That's what makes it so much fun!
Posted 13 Jul 2010 at 2:22pm #
""An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff.""
This was THEIR adaptation of the myth, because they realized the impossibility of the ACTUAL premise of the myth. So what they set out to do was simply see if a treadmill could keep a plane from taking off. It cannot.
Posted 13 Jul 2010 at 2:36pm #
If there was a headwind of 200mph and the plane was flying at 200mph, the ground speed would be 0. It would appear stationary to the ground, yet flying at 0 mph.
Ground speed and air speed are 2 different things.
The thrust is against the air so it doesn't matter what the conveyour belt is doing.
Depending on how the question is worded (depending where you read it), it will either take off and the conveyor can do nothing about it, or by moving it will break the rules of the question.
Posted 13 Jul 2010 at 2:49pm #
JCBoston69 said on July 13, 2010:
Who is "they" in "THEIR"? MythBusters? Because they didn't "change" the myth at all. They tested the myth accurately and proved that the plane can take off.
Again, with no wind, ground speed and air speed remain the same. If you didn't know the plane was on a conveyor belt, takeoff would appear perfectly normal to an observer on the ground. It'd appear normal to a person in the plane, too.
A plane can take off on ice. Wheels (bearings) and a treadmill are basically like ice - largely frictionless and thus powerless to stop a plane from pulling itself forward through the air.
MythBusters tested it properly and got the correct results.
Posted 13 Jul 2010 at 4:11pm #
"They tested the myth accurately and proved that the plane can take off."
They tested it accurately after eliminating the impossible aspect of the myth, matching the treadmill speed to the speed of the plane.
Posted 13 Jul 2010 at 4:41pm #
"This was THEIR adaptation of the myth"
This whole website is in response to the results of MythBusters testing of their adaption of the myth. No matter what the original wording of the myth, and who knows how long the question has been out there, they developed ways, as best they could, to test the dynamics involved.
The plane is the center of the controversy. The "spirit" of the myth, or the "actual premise of the myth", as you put it, does not exist because the plane CANNOT remain stationary to the ground on the treadmill. Otherwise, you might as well use a car, or a jogger, or a bicycle, and so forth, whose speed CAN be matched by the treadmill, and will remain stationary relative to the ground. Maybe if you could somehow stick a motorized propeller and wings on them they'd take off...but that's too bizarre!
That's why I don't belive there is any other version, or wording, of this myth that makes any sense. Those who do are just adding their own spin to cover up their initial snap judgement. I know because when I first saw the show I said to my wife, "Look, the plane is moving forward. The test is flawed." After I thought on it, however, I said, "Wait a minute. Of course it's moving forward. It has to."
MythBusters got it right!
Posted 13 Jul 2010 at 6:29pm #
Ok, I've been reading these posts (not all of them, but many) and my brain is exhausted from all the bickering.
So let me get this straight.
We have 2 possibilities/explanations/situations, as far as I can tell.
One, where the airplane is, in some manner, tied to the ground Preventing forward, but not vertical, motion. Under the airplane is a treadmill. The treadmill accelerates to some speed, forcing the airplane to accelerate as well or else be pushed off the treadmill like a jogger to has lost his footing. But the airplane remains stationary, no matter the speed of the treadmill; like someone holding onto the bars of a treadmill. Treadmill spins, and the legs are flapping to keep up, but at a speed equal to the treadmill.
And then theres the second scenario; where the airplane is not tethered to the ground while on the treadmill and is allowed to accelerate to any speed it can, regardless of what the treadmill is doing underneath it.
As far as I can see, in the first situation, the airplane has no airspeed, (as well as no ground speed). Therefore, no lift. Therefore no flight.
Whereas, in the second scenario, the airplane is able to freely accelerate to a greater velocity than the treadmill/conveyor is capable of. Therefore gaining forward motion, allowing for some amount of airflow over the wings and therefore, an airspeed, and incidentally, a forward ground speed. In which case, the airplane (or the people within) would not know that there is a conveyor beneath them. This forward airspeed would allow for lift/flight.
So it seems to me that for the Mythusters experiment, one would have to choose between the 2 scenarios. Where in (A) an airplane being prevented from moving is not an airplane, and therefore would be a false premise. or (B) where the airplane is free to do what it wants/can, therefore negating the premise of the myth.
So thats how I see it. If thats wrong, I'm sorry. Be nice. This isn't a forum to get snarky and mean. I don't think Adam or Jaime would appreciate seeing it.
Posted 13 Jul 2010 at 8:18pm #
me said on July 13, 2010:
That's not a possibility at all. Not one bit. It's not even worth discussing - why would a plane be tied to the ground?
me said on July 13, 2010:
Nope. The speed the treadmill is "capable of" is irrelevant. The plane takes off regardless of the speed of the treadmill - not because it's "going faster than the treadmill is capable of."
Heck, make the treadmill go twice as fast as the plane - it'll still take off. The wheels will just spin three times as fast as they normally would.
me said on July 13, 2010:
There's no negation of anything... Where? MythBusters tested the myth properly. There's no negated premise - there's a plane on a treadmill. That's the premise. The "matching speeds" bit of the "premise" is just there to trick people who think a plane accelerates the way a car does.
me said on July 13, 2010:
They didn't invent the myth. They just re-popularized it.
Posted 13 Jul 2010 at 9:21pm #
Me,
Sorry! Erik is correct. The basic question is quite simple. The rest is stuff people think up to try to explain something their mind has trouble grasping.
Go to this website to see MythBusters' original statement of the myth,
and their attempt to demonstrate it. It may not be a perfect demonstration, but it is probably as close as anyone will get without building a mile long treadmill that can support an airplane.
mythbustersresults.com/episode97
Of course, you don't need a demonstration. Logic will do just fine.
Posted 19 Jul 2010 at 9:20pm #
I guess I must be one of those "stupid" people, because, I still don't get it. It may have been mentioned before, but it seems to me if the plane were on a treadmill, and thus not moving forward, there wouldn't be enough air flowing over the wings to achieve lift. I too saw the episode and it appeared the plane was in fact moving forward, that's why there was enough lift for the plane to take off.
Posted 19 Jul 2010 at 9:25pm #
for those of you who want more info: check out this link: http://www.airplaneonatreadmill.com/
Posted 20 Jul 2010 at 7:55am #
Steve said on July 19, 2010:
"Thus" is used to precede a logical conclusion.
That the plane is not moving forward is not a logical conclusion. The plane moves forward because the engine (props, jets, whatever) pulls itself against the air, not the ground like a car or bike.
Posted 20 Jul 2010 at 10:44am #
Steve,
You have reached a correct conclusion to an incorrect premIse.
"IF" the plane were rendered "stationary" by the treadmill, it would indeed not take off. However,(now this is very important) the plane CANNOT remain stationary, no matter how fast the treadmill is traveling backward, because the treadmill does not effect the forward motion of the plane, brought about by it's propellers PULL THROUGH THE AIR! The wheels are not dependent on a surface to create forward motion, like a car, bicycle or feet. It just needs the air.
The challenge makes no mention of the plane being stationary. Most "no fly" proponents just assume this. That is the whole reason for the controversy. The situation, to some, is counter-intuitive, and that is what makes it appear to be a trick question.
Posted 20 Jul 2010 at 7:22pm #
This quote seems to be the best way to describe the reasons people "don't get it".
"You see, the confusion all arises from misses - misconceptions, misinterpretations, and misunderstandings. Consider three rewordings of the question:
1) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I begin to attempt to take flight in the plane, and you attempt to match my speed to try to keep me stationary. Will the plane take off?
2) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I throttle up the airplane and you turn on the treadmill, and we conspire by our joint effort to try to keep the plane stationary relative to the ground. Will the plane take off?
3) An airplane is sitting at rest on a very powerful treadmill. You are at the controls of the treadmill, while I am at the controls of the airplane. On some signal, I attempt to take flight in the plane, but you match my speed with the treadmill and keep me stationary relative to the ground. Will the plane take off?
Posted 20 Jul 2010 at 8:19pm #
Steve said on July 20, 2010:
The problem with that is that a treadmill cannot keep a plane stationary.
Posted 21 Jul 2010 at 11:12am #
That's why a conspiracy to keep the plane stationary is necessary. the pilot would throttle the plane to only the amount necessary to counter the friction of the wheel bearings.
Posted 20 Jul 2010 at 9:44pm #
If he starts the treadmill before you throttle up, you will move backwards. As soon as you throttle up you will move forward relative to the ground and the treadmill. There is no way to keep the plane stationary no matter how fast the treadmill is moving. Only if the treadmill is NOT moving, and the engine is off.
Posted 21 Jul 2010 at 9:19am #
Since this string is in response to MythBusters' attempts to either prove or bust this myth, the only wording that should be considered is theirs. This is how the myth reads, taken from their websight:
""An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff.""
No "stationary to the ground", no "pilot speeds up while treadmill speeds up", no "spirit of the challenge". It's a matter of physics, and fairly simple physics, at that!
Since the guys on MythBusters demonstrated in several ways, to the best of their abilities, that the plane will move forward and take off, they succeeded in busting the myth. fini
Posted 21 Jul 2010 at 11:14am #
The question is simpler than that. Most people simply are concerned with the question as to whether or not a treadmill can prevent a plane from taking off.
The answer is no, at any speed.
Posted 21 Jul 2010 at 12:52pm #
"(EDIT: Really, you should substitute the word "air" for ground in the above facts. I use "ground" throughout this post because of a consistent mistake made by "no-flys" in their assumption that the plane remains stationary. It doesn't remain stationary, relative to the ground or the air. The important point is that it moves relative to the air, not the ground, but I'm assuming throughout this post that there is no significant tailwind or headwind. I discuss the implications of this briefly in the section about windtunnels.)"
I agree with using "ground" as opposed to "air" (because air is not stationary, by nature) or "treadmill" (because the treadmill is moving, but is presumably on top of or parallel to the ground).
Posted 02 Oct 2010 at 3:25am #
Imagine an aircraft carrier going 50 mph. A plane requires a speed of 50 mph to achieve liftoff. The carrier is going west and the plane is going east. If the "no-flys" were correct, then the plane would need to go 100 mph to achieve liftoff. This is not the case as proven everyday in the navy. The plane simply goes 50 mph and is airborne because it does not rely on friction with ground to move as cars do (try driving on ice, you dont go so fast even with power output.) Instead, it propels through air except for the friction from the wheels which is negligible. The aircraft carrier is no different than the conveyor belt in this case.
Posted 03 Oct 2010 at 3:57pm #
Greg said on October 2, 2010:
I agree with your end result but you're wrong: an aircraft carrier can affect airspeed, which is why they try to launch planes in the same direction as the carrier is traveling.
Posted 03 Oct 2010 at 11:13pm #
yea but you could say the same thing about the wind movement generated by the conveyor belt...obviously it is at a much lesser scale but there is still some wind movement which technically could affect the plane in very minute ways. The aircraft carrier definitely exasperates the wind change, but the concepts are still equivalent. I do agree though that the AC will definitely affect the plane because of the air displacement caused.
Posted 03 Oct 2010 at 11:47pm #
Greg said on October 3, 2010:
In a word, Greg, no.
Posted 04 Oct 2010 at 12:00am #
haha, fair enough
Posted 04 Oct 2010 at 2:44pm #
Greg said on October 2, 2010:
The first part is right. If an airspeed of 50mph is needed, and the ship is going through dead air at 50mph (generating a deck-level airspeed of 50mph), the plane WILL take off temporarily (if it's not tied down, which I assume it is, as the large gusts of wind common at sea will move planes about the deck). If the same conditions exist and the plane goes in the opposite direction, it will require 100mph in relation to the deck (50mph airspeed). The only way a plane could take off in the opposite direction at 50 mph deck speed is if there is a 50mph tail-wind.
Why you got off track is beyond me.
Posted 04 Oct 2010 at 3:03pm #
No, you're wrong, my concept was right the only problem is that in reality the aircraft carrier displaces the air while it moves so it changes a bit. But the concept is still correct.
Posted 04 Oct 2010 at 3:15pm #
Changes a BIT is the key phrase here. Planes take off into the wind for a reason, and THAT is the reason.
Posted 04 Oct 2010 at 3:43pm #
They take off into the wind because the lowers the ground speed necessary to achieve liftoff. The wind caused by the AC moving 50 mph the opposite direction is not equal to 50 mph wind going the opposite direction.
Posted 04 Oct 2010 at 3:59pm #
Right...but if the "ground" is moving in the opposite direction at the speed the plane needs to take off, then the plane needs to be moving twice as fast relative to the "ground" to take off.
Posted 09 Oct 2010 at 2:41am #
JCBoston that is incorrect, the plane needs to be moving at take off speeds in relation to the AIR around it...
A plane needs force pushing it forward in order to take off. The point of the conveyor belt is to theoretically provide enough force in the opposite direction to prevent the plane from moving forward.
However, the lateral force of the treadmill (We'll call this "Backwards" from now on) is transfered to the wheels as rotational force (IE the wheel's spin). A very small portion of this force is transfered to the airplane through the friction in the bearings of the wheels. With 0 thrust from the plane this force would cause the plane to begin moving backwards. This force transfered through the bearings is the ONLY thing pushing the plane backwards. It is a miniscule fraction of the force provided by the conveyor belt.
When the plane begins providing forward thrust, this provides a "forwards" force which is opposite and competes with the "Backwards" force generated by the belt.
The bearings cannot, and will not, transfer enough "Backwards" force into the plane to overcome the forward thrust. Even if you had bearings that defied the laws of physics and could transfer that much force without falling apart, the wheels themselves could create enough friction to stop the plane.
Without breaking the laws of physics the conveyor belt could NOT stop the plane, at any speed, because the force of the conveyor belt cannot be transfered to the plane.
Take a wheel on a stick, and hold the wheel down on a moving tread mill. Now push the stick forward to cause the wheel to roll up the treadmill. See how little force it takes? Take your hand and slide it up the moving treadmill (Don't actually, you could hurt yourself). It's quite difficult. This is because with the wheel, nearly all of the force from the treadmill is transfered into rotating the wheel. Your hand however, has lots and lots of friction compared to the bearings, and does not rotate, so lots of the treadmill's force is transmitted into moving your hand backwards.
Put in a single sentence, "The bearings prevent the conveyor belt from transferring enough force into the plane, to overcome the thrust and prevent the plane from moving forward."
Posted 09 Oct 2010 at 9:27pm #
"JCBoston that is incorrect, the plane needs to be moving at take off speeds in relation to the AIR around it..."
That's exactly what I said. My suggestion is that you work on reading comprehension.
Posted 10 Oct 2010 at 1:21am #
"plane needs to be moving twice as fast relative to the "ground" to take off."
I suggest you work on writing.
Posted 15 Oct 2010 at 11:39am #
My writing is fine, and if you've read all my posts instead of just the last one (if it seems at all ambiguous, you should have maybe told me that rather than ASSuming anything), you would know EXACTLY where I stand on the issue.
Anyway, nice comeback. It's pretty consistent with your overall quality.
Posted 15 Oct 2010 at 12:22pm #
So JCBoston, you said, "My suggestion is that you work on reading comprehension." However, he read it correctly and it was you who wrote it incorrectly. Yet you think he is the ass for defending himself against your undeserved insult? I read your other comments and knew you either didn't understand the true reasoning or mistakenly wrote it and i didnt care to respond but the correction by LazyLemmings was completely justified because you did get it wrong.
Posted 15 Oct 2010 at 1:16pm #
I may have not been clear in ONE post. However, ALL of my posts from over the years are still here, and if Lazy (apropos name if there ever was one) bothered to read it, he wouldn't have wasted his time.
And I didn't write it wrong. I said it has to be the plane relative to the air. My reference to the moving ship might have confused you, but it wasn't wrong.
If the ship is moving through dead air at 50mph, the plane needs to be moving in the other direction at 100mph relative to the ship (which, if your powers of inference were up to snuff, you would easily see means an AIRspeed of 50mph). It's NOT rocket science people.
Posted 16 Nov 2010 at 4:28pm #
Similar question I've seen about.
Imagine a plane is sitting on the beginning of a massive conveyor belt type arrangement, as wide and as long as a runway, and intends to take off. If the conveyer belt exactly matches the speed of the wheels at any given time, but in the opposite direction of rotation, can the plane take off? There is no wind.
Opposite answer though.
Posted 16 Nov 2010 at 11:29pm #
Nathan said on November 16, 2010:
That's a lousy variation of the question though, because if the wheels precisely match the speed of the belt at any given time then the plane is idling, tied down, or otherwise not even trying to take off.
Posted 07 Dec 2010 at 7:26pm #
Except for one thing... they never established that the tarp could be moved with the plane remaining stationary, as would be the case with an actual conveyor belt. Considering that the tarp ripped when Adam ran across it, it's pretty obvious that it lacked the strength required to act as a conveyor with an airplane upon it, which is an integral element of the myth. The tarp simply had no effect, as the truck and airplane move simultaneously at the same speed and so the tarp simply passes under the wheel of the airplane. IT NEVER ACTS AS A CONVEYOR.
I think their conclusion is correct, but it should be evident to anyone watching that this experiment was very flawed in its execution and does nothing to prove that a plane would take off in the conditions described in the myth.
Posted 07 Dec 2010 at 8:49pm #
Aaron said on December 7, 2010:
That's wrong; the plane does not remain stationary.
Posted 07 Dec 2010 at 9:31pm #
Stationary as in not moving under it's own power, but solely under the truck/tarp's. Like I said, the tarp never acts as a conveyor.
Posted 07 Dec 2010 at 9:43pm #
Aaron said on December 7, 2010:
I'm not sure why it matters that the tarp can move while the plane is stationary. That's not in the problem - the tarp matches the ground speed of the plane. If the plane is stationary, so is the tarp.
Posted 07 Dec 2010 at 10:09pm #
Erik J. Barzeski said on December 7, 2010:
I think you're misunderstanding my point (or I'm not expressing it clear enough); my point of contention isn't that the tarp can move, but rather that it doesn't seem to drag the plane and create conditions where the actual ground speed is where it is supposed to be... it does not act as a conveyor belt would. At no point do they test the strength of the tarp to ensure that it can pull the plane with the assistance of the truck. If the tarp can't pull the plane (which would seem to be the case, since it rips when Adam runs across it, Adam being of considerably less mass than an airplane) it isn't acting like a conveyor belt... the tarp should be able to support the mass of the airplane (and move it when attached to the truck) without requiring the airplane to move on its own power... otherwise the force required to overcome it is negligible. This is indeed an integral part of the problem, one which having a tarp merely pass under the wheels of the plane does not account for; they're basically just pulling tarp under the wheels of the plane and creating very little resistance in the opposite direction in terms of ground speed.
Think of it this way; the experiment worked with the model plane because the material could hold the lightweight model in such a way that it would drag it when external force is applied; the ground speed in effect matches the takeoff velocity as it is supposed to. Had they used something of insufficient strength, and instead had the model airplane and the other vehicle move at the same time, the ground speed would remain close to normal because it would have little to no effect on the on the motion of the plane while at rest. The methodology of their final experiment is flawed.
Posted 07 Dec 2010 at 11:03pm #
once the plane starts moving there is so little friction between the wheels and the tarp that i hardly see that as mattering...correct me if im mistaken but it seems like you are saying they should have taken into account something they know wouldnt effect the experiment.
Posted 08 Dec 2010 at 9:44am #
blockhose said on July 13, 2010:
This is exactly what I meant. (And I appreciate you posting this) That the velocity and acceleration were clearly NOT matched by the belt, or the plane would have shown no movement, and it clearly did. With the plane showing movement forward, rather than staying stationary while the engines propelled it, you're now testing what little amount of distance a plane must travel forward to take off. I know very little about physics, but it sure doesn't take someone who KNOWS about them, to realize that experiment was flawed. The premise of the experiment was to match the conveyor belt speed to that of the moving plane with the engines on, propelling it. There is no excuse for the belt not matching the speed that the engines were propelling it, other than sloppy experimenting.
The belt cannot have a constant speed of being pulled in the opposite direction, because the plane's engines do not have a constant speed of propulsion. Assuming that cars and jet engines propel at the same speed is ludicrous, which was an accepted value when they pulled the tarp by means of a vehicle (If I'm not mistaken).
I want to think it's more complicated than that, but I can't. I read and try to understand everyone's explanations, but I just believe it's more simple. I'm not saying a plane is unable to take off on a conveyor belt. I'm saying the experiment was wrong for trying to prove it can or it can't. I don't know why anyone would deny that.
If you care about science, you shouldn't go in rooting for the experiment to go either way. Sure, you have an assumption about what will happen, thus the purpose of a hypothesis. But they didn't approach this myth unbiased. Instead, they went in with the desire to prove something would happen, and flawed the dynamics of the experiment in the process, to accommodate their theory. You're a scientific referee, not a bookie.
Posted 08 Dec 2010 at 1:53pm #
OK, just because you cant understand the explanations does not mean that it has to be more simple than that. The fact is, the experiment was a success. The thing you overlook is that the plane's wheels barely experience any friction with the conveyor belt so the conveyor belt can be going the same velocity as the plane but the plane will still take off because it is propelled by friction with the air. They did not flaw the dynamics of the experiment, the plane took off exactly as it should given the myth's conditions. Even if they were flawed somehow in their experiment, which they were not, but even if they were, there is nothing they could have done that would have made it act diferently while still following the guidelines. But if you couldnt understand that after reading Erik's comments then i cannot imagine i can convince you because a 3rd grader could understand his straightforward logic which perfectly explains why Mythbusters were right.
Posted 08 Dec 2010 at 2:19pm #
Colleen said on December 8, 2010:
Colleen, you're wrong. The plane does not stay stationary for the same reasons that a roller skate on a treadmill being pulled by one of its laces can go forward even if the treadmill is moving 100 MPH in the opposite direction.
Posted 08 Dec 2010 at 3:35pm #
Why would the roller skate move forward, unless the velocity of the treadmill moving at 100mph decreased? I don't think a roller skate being pulled on a level treadmill at 100mph would exceed the speed of 100mph and travel even faster on it's own to move forward? I don't think I understand your analogy. In theory, the roller skate would ALWAYS be traveling forward, however, if it's rate of speed is matched by the treadmill, I wouldn't think it should move at all. Where would you get the added inertia to coax the skate either forward unless the treadmill couldn't match speed? Energy can't be created or destroyed, so where would it come from to push the skate over 100mph to actually move forward? Not to mention, we're talking about a skate...not a jet-engine powered skate.
And once AGAIN, I'm claiming the experiment could go either way with an acceptable percentage of error. And yet the experiment had too much error to be conclusive. I'm eager to track down this myth and watch it again to pull quotes from the Mythbusters themselves. I remember the plane being stationary (which in the footage, it clearly is not), being a large part of the myth's mystery.
Posted 08 Dec 2010 at 9:53pm #
Colleen,
You have based your conclusions about this myth on an incorrect premise. Nowhere is it stated on the show that the treadmill has rendered the airplane stationary. That is YOUR presumption, as well as many others who believe that the tests run on Mythbusters were flawed. The myth in question is as follows:
"An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff."
This is taken directly from the episode, which can be viewed at the following website:
mythbustersresults.com/episode97
It is, in fact, a physical impossibility to keep a free-wheeling plane stationary, relative to its' surroundings, no matter what surface it's on. Once those props are turning it's going to go forward unless it has something holding it in place, like breaks, on a stationary surface. In this case, however, it would just move backwards with the treadmill.
It is understandable that some people have a hard time grasping the point that a plane functions differently than a car, a bicycle or anything else that is dependent on surface friction for its' locomotion. A plane uses the air.The ground just supports it until it reaches sufficient speed to go UP. The treadmill WILL NOT CAUSE IT TO APPEAR STATIONARY!!! This was never intimated anywhere!
No "velocity and acceleration of the plane are matched by the belt, such that the plane is stationary relative to the ground", no "pilot speeds up while treadmill speeds up", no "spirit of the challenge". It's a matter of physics, and fairly simple physics, at that!
Someday a light may dawn in your brain as to what this challenge is all about, as I have personally witnessed happen to many, many naysayers once I kicked the "stationary" notion out of the way.
Since the guys on MythBusters demonstrated in several ways, to the best of their abilities, that the plane will move forward and take off, they succeeded in busting the myth. fini
Posted 17 Dec 2010 at 7:20am #
Can I just say that anyone who even remotely thinks that a conveyor belt will stop a plane from taking off has obviously no idea of how lift is produced in an aircraft or how an aircraft works and doesn't even deserve the energy required to try convince them otherwise. Your all idiots! Especially that Tom guy!!
Posted 19 Dec 2010 at 9:50am #
Anyone who is still not sure what's going on, please watch this video:
http://www.youtube.com/watch?v=bEyfHwDdXSg
Thank you!
Posted 20 Dec 2010 at 6:08pm #
Had an Air Force captain, a pilot, in my place of business recently. He thought the plane would not take off. SCARY!!! He finally admitted he was wrong after I queried him about it. As with most, his snap judgement and presumption did him in.
Posted 28 Dec 2010 at 12:20am #
The only thing a conveyor or treadmill going back wards at x mph is make the tires of the plane spin x mph faster as they are the only things that are affected by it. Planes don't need ground to operate, moving or not.
Posted 29 Dec 2010 at 11:57am #
Steve said on December 17, 2010:
Irony?
Posted 04 Jan 2011 at 10:38am #
JCBoston69 said on December 29, 2010:
Not irony...delusion!!
Posted 17 Jan 2011 at 4:07pm #
Read number 3. It explains that they didn't do the experiment correctly and re-did it even though they didn't air it. A PLANE WILL NOT FLY WITHOUT AIR OVER ITS WINGS!
http://dsc.discovery.com/fansites/mythbusters/top-ten/mythbusters/myths-about.html
Posted 17 Jan 2011 at 4:22pm #
Mike said on January 17, 2011:
Uhm, brain fart alert. I really hope it's just a brain fart, because the point of that page is to share the "top 10 myths about Mythbusters."
If you click through to page two you can read this:
The myth about Mythbusters - the one you accepted as "explained" - was busted. They stand by what they proved.
Of course a plane won't fly without air over its wings, but that ends up being irrelvant to the discussion. The plane moves forward because the jet engine, propeller, etc. pulls the plane through the air… as has been explained a few thousand times already.
You've not only got the original answer wrong, but you've misread a post that's further proving that original (correct) answer as if it supports your incorrect conclusion!
Classic!
Posted 17 Jan 2011 at 6:38pm #
Mike said on January 17, 2011:
Actually, Erik, I liked your reply so much I thought it needed repeating. Maybe Mike will eventually "get it"!
Anyway, Mike, you've got it all wrong, but I refuse to keep repeating what is so obvious to most thinking humans.
Which brings me to #1 on the same list you pointed us to, where they state the Jamie Hyneman is a robot! Should we take THAT as gospel?
Posted 18 Jan 2011 at 12:37am #
Ok watched it again tonight, and have been following several forums on the topic. Originally, when it aired, I scratched my head thinking how could they possibly call that "Busted" because the plane is clearly moving forward. But now I understand the fallacy of my presumption that the plane cannot move forward.
The whole setup of the myth leads many to believe what they are going to "attempt" to do is keep the plane stationary by matching the tarp speed to the planes take off speed, and the plane will magically hover for a few seconds from a stationary position, and clearly that cannot and will never happen.
When it comes down to it , its a good trick question posed by Mythbusters. The "no flys" , including myself , were fooled in assuming what they meant was flying from a stationary position at take off throttle - this obviously cannot be done.
The "no flys" (again including myself at one point) cant get past the fact that the underlying myth is not about keeping the plane stationary, its about PREVENTING the plane from moving forward, which I now understand you cannot do by pulling the tarp underneath it.
If the myth were restated such that : "If you had a treadmill with unlimted speed potential and moving in the reverse direction of the plane, can you prevent a plane from moving forward? Or a rocket powered car, or a jet fighter ?" The answer is NO you cannot prevent it from moving forward regardless of how fast the treadmill is going as long as the potential energy of the plane , rocket car or jet has enough power to overcome only the little friction that the wheels present. And as long as the plane can move forward it will eventually move fast enough to fly, because thats what planes do.
So in the end the trick that fooled me was believing that you could actually prevent a plane from moving forward in the first place under those conditions !
Posted 28 Jan 2011 at 7:18am #
Glad you have seen the light, Kris. I would not exactly call this a "trick" question, however, as in "If a rooster lays an egg on top of a barn, which side will it roll down?", or "How many animals did Moses load into the ark?", because when you tell people the answer they understand immediately that the question was misleading.
Many people, as we have seen, will argue the results to Mythbusters expeiments, and try to change the wording of the myth itself to prove their beliefs as to what the answer SHOULD be.
Since this sight was created to discuss the results of the experiments conducted on the show, we should stick to their wording of the myth. The wording does not mislead in any way. People just reach the wrong conclusion because they, as you said, presume the plane is stationary, or they just don't understand how an aircraft flies.
Understandable, really, unless that individual is a pilot, and I have met several. Very disturbing!!!
Posted 28 May 2011 at 12:18pm #
Rerun just aired, so I figured I'd resurrect this discussion (even though I'm sure people have probably already said pretty much the same thing above.)
To quote the pilot at the end of the show when asked to predict if the treadmill will prevent him from taking off:
"Yes, if I match my speed exactly the same speed forward as it's going backwards and there's no air over the wings, I should just sit there like a brick."
So, while the myth should be (is) about whether or not the plane moves forward (which it clearly does) and anyone that gives enough thought about it would come to that conclusion, it is also entirely ridiculous to state that the show presents the myth in absolutely consistent terms. IF he WERE to match his speed exactly (even though this obviously doesn't happen when providing normal power to the propeller), then, as everyone consistently states, he of course wouldn't be moving relative to air and would of course not experience any lift. So his statement wasn't wrong (even though the show acts like it was), it just wasn't on point.
This is just one example where the Mythbusters presentation blurs the line between two interpretations of the myth. And such blurring is the source of 99.9% of the confusion on all of these forums. (And yes, that statistic is made up.)
Posted 30 May 2011 at 8:55am #
JimJoeBob said on May 28, 2011:
The problem with your entire rant is that there are not two interpretations of the myth. There aren't. You could move the conveyor belt at a 1000 MPH - the plane will still roll forward because its forward motion is not governed by the wheels.
The "matching the same speed" is the mental hurdle in understanding the true physics of the question. It's the "stumper" part. Once you realize that a plane's locomotion has nothing to do with the wheels (the only thing touching the conveyor belt), then you "get it" and you can get the right answer.
There are not "two versions." And if there are, it's "people who understand the question and people who don't understand the question."
Posted 30 May 2011 at 11:57am #
Fair enough Erik...I'm not purporting that there are two equally interesting (or even valid) "myths". I'm just suggesting that some of the phrasings used in the show are what has led to (much of) the confusion you've been helping people overcome. Thanks for the reply!
Posted 30 May 2011 at 12:05pm #
JimJoeBob said on May 28, 2011:
All this proves is that the "pilot" didn't understand the physics involved in the operation of his own plane, and that's the scary part!
Posted 31 May 2011 at 10:13am #
Hmmm...I don't know that my example "proves" anything, but I do think it supported my overall hypothesis that there are (what I called) inconsistencies in the presentation of the episode that may have led to some of the confusion seen on this forum.
The facts are clear: The pilot made a true statement and after the experiment, the show indicates that he had made a false statement. I don't care why he made the statement, what question he thought he was answering, what he really meant, whether his statement addresses any point that we care about, etc. All I care about is that carefully parsing his words reveals a true statement. IF he WERE to match his "speed exactly the same speed forward [relative to the treadmill] as it's going backwards [relative to ground] and there's no air over the wings, [he] should just sit there like a brick." Later treating this statement as false is an error.
That's the only point I'm making with this example. Again, I don't care if his statement was nonsense from the perspective of what really happens when the propeller is operated. He made a true statement and Mythbusters indicated it was false.
This example is given only to support my opinion that inconsistencies such as this one are the source of much of the confusion here and that most people aren't arguing physics but rather semantics.
Posted 31 May 2011 at 11:37am #
JimJoeBob said on May 31, 2011:
The problem is that the pilot did not make a true statement. I've bolded the incorrect parts:
"Yes, if I match my speed exactly the same speed forward as it's going backwards and there's no air over the wings, I should just sit there like a brick."
That part about the plane sitting still (no air over the wings) is false in the context of the question. He misunderstood (frighteningly so) how the physics of a plane's takeoff work. He made the same dumb mistake others have made.
The show did not misrepresent the pilot or his answer. The pilot simply got the answer wrong (like many other people) because his reasoning was wrong. He didn't give a true statement.
Posted 31 May 2011 at 2:39pm #
Erik, I'm not concerned with the "context of the question."
This is simple mathematical logic. The pilot made a statement, "if A then B". For this statement to be true, all that is required is that B is true whenever A is true. I don't care that A isn't true in the "context of the question." That is irrelevant to the logical truth of the statement.
Posted 31 May 2011 at 3:02pm #
JimJoeBob said on May 31, 2011:
It's fine if you want to do that. To each his own, regardless of how dumb or pointless…
The entire show was about the context. It was about answering the question, determining the veracity of the myth. He was asked if the plane would take off and he could have just as easily answered "no, because my aunt's name is Jemima." He'd be "right" in stating that his aunt's name is Jemima but he'd still get the question wrong.
You can't say context is irrelevant, then claim that some of the context - the part in which they say "the pilot was wrong" - matters.
Edit: Previous math-based reasoning replaced with one that makes more sense.
Posted 18 Dec 2011 at 2:13am #
He's right. I happen to be a mathematician, and technically, the pilot said: 'a lack of the plane's motion' IMPLIES 'the plane will not move and therefore won't take off.' The statement is true. I get what you're saying: the plane DID move, and therefore DID take off, but the statement is still technically true.
Posted 23 Jun 2011 at 12:08am #
The plane will obviously move forwards and eventually take off. Let me explain. If the engine of the plane is off, yet the conveyor belt is running, we can all agree that the plane will move backwards because there is no propulsion thrusting it forwards. The same will happen in this scenario if you replace the plane with a car, right? If the car is traveling at the same speed as the conveyor belt is in the opposite direction, the car will remain perfectly stationary because the car's source of propulsion is in contact with the conveyor belt. A car relies on moving the road backwards (relative to itself), yet the "road" is already moving backwards. However; if the plane is traveling at the same speed as the conveyor belt is in the opposite direction, the plane will move forwards regardless the fact that the tires move backwards because the plane's source of propulsion is NOT in contact with the conveyor belt, making it irrelevant. A plane relies on moving the air backwards (relative to itself), NOT the ground. Turn a bicycle upside-down so that the tire is not touching the ground. Imagine that the air's relation to the tire is the plane's relation to the tire. Did the bike move?
Posted 04 Jul 2011 at 11:24am #
It appears to me that the people who are posting on this site and others fall into three categories.
1) Those who "get it," and understand that there is a major blind spot causing some individuals to arrive at an incorrect conclusion.
2) Those who don’t "get it," and stick to the premise that the plane behaves like an automobile or jogger. That is, will somehow remain in place when the speed of the plane and the treadmill are matched.
3) Those who initially began as category 2s, but later realize they are wrong. These people are most interesting because rather than outwardly "jumping ship" they stick to their original declaration, and try to convince others that there is an underlying "spirit" to the myth that substantiates their claim.
I could argue that there is a 4th group of individuals who belligerently declare that it is a stupid myth and we shouldn't even be discussing it. Evidently, the hundreds of postings we have seen disprove that position. If nothing else, it is an intriguing insight as to how people perceive and go about solving a brain teaser.
Posted 13 Jul 2011 at 9:44pm #
really, a two old year argument? I don't believe people who advocate the "plane on a conveyor belt will not fly" side would be convinced otherwise unless someone built, at the cost of millions of dollars, an actual runway sized conveyor belt and ran the experiment.
Since that would be a senseless waste of money to prove something most people already "get", this will have to remain a thought experiment that drives many people to humorous distraction.
Posted 29 Jul 2011 at 11:28am #
Alright. All analogies aside, it looks like this discussion has gotten away from the original myth.
The Mythbusters' idea for conducting this experiment was to take a propeller driven plane and put it on a treadmill. If the plane took off, myth busted. If the plane stayed still, myth plausible.
During the design of the experiment, there was an animation showing how busting this myth was supposed to work. The treadmill would start, the plane would turn on it's propeller, and the plane would either lift off of the ground right where it was, or not. Again, that was in the animated presentation before the actual experiment.
When the Mythbusters actually conducted their experiment in full-scale, the plane did not stay in the same place on the treadmill. It moved forward, lift was generated, and the plane took off.
Now, since the myth claimed it was impossible to take off on a treadmill, myth busted. The plane was on a treadmill, then it took off. The fact that it moved forward and had adequate lift is irrelevant.
Posted 26 Sep 2011 at 4:24am #
I just watched the episode and still didn't understand. I didn't really doubt the conclusion, I just couldn't understand it.
I think things would have been better to understand if the Busters had mentioned that the wheels on the plane are, in fact, going 50 miles an hour, because the treadmill only adds to the forward moment that the engine generates due to the nature of wheels on a plane being free.
That's what confused me, I thought that the wheel's speed was matching the conveyor belt.
Posted 08 Dec 2011 at 4:21am #
The whole point of debate is to challenge each other's assumptions and help each other learn.
Calling people "stupid" and other vitriolic things might make you feel better about yourself, but anti-social remarks like are not in the spirit of discussion, even if you do hold the opinion that certain people are stupid and idiots.
Posted 08 Dec 2011 at 4:54am #
And yes, I understand clearly why the plane takes off, but some of you guys' attitudes are appalling. You're right. Get over it.
Posted 18 Dec 2011 at 1:58am #
I enjoy looking at an argument and then arguing both sides. This is a kind of problem where there should be only one right answer, and the right answer as it appears in the natural world is that the plane will take off--the conveyor belt will cause no impedance to the forward velocity of the plane (but more on that later). However, the no-fly camp is correct in a way.
The no-fly camp assumes that the plane is held from moving forwards by the conveyor belt. This is essentially false: the conveyor belt provides no impedance to the forward velocity of the plane. However, they believe that the spirit of the problem is that by some means the plane is prevented from moving forward and yet is still allowed to take off if it receives the necessary lift. If the problem is interpreted this way, then it is true that the plane will not take off, as no wind is moving over the wings (and the wind created by the propeller is negligible), and therefore there is no lift, and the plane sits there like a rock.
The take-off camp doesn't take that the plane is held still as a given. In fact, that is their essential argument: the conveyor belt has no affect upon the speed of the plane whatsoever. This means that the plane will still move forward in spite of the conveyor belt and, because there IS air moving over the wings in this case, the plane takes off. The reasoning behind this is deceptively simple, but first, we will contrast the plane with a car. With a car, the motor sends power from the engine into the drive train into the drive wheels. These wheels then exert their rotational energy on the surface below them, and this makes the car move forward. If a conveyor belt is placed below the car, it will be held stationary because the tires' velocity in relative to the ground determines the actual velocity of the car (meaning that the velocity of the car is determined by both the velocity of the tires and the velocity of the conveyor belt). This means that the velocity of the tires will cancel with the velocity of the conveyor belt and the net velocity of the car is zero. The plane is different. The plane's engine sends its power to the PROPELLER, not the tires, and the propeller spins, pushing the wind back, and therefore pushing the plane forward. The velocity of the plane then determines the velocity of the tires. So, where the car's velocity is the speed of the tires in relative to the speed of the conveyor, the speed of the plane's TIRES is the velocity of the PLANE in relative to the velocity of the conveyor belt. The speed of the plane's tires in relative to the speed of the conveyor belt is meaningless, as the tires are design for no other purpose than to reduce the friction between the plane and the ground. Since the friction of the wheel bearings is negligible, the speed of the conveyor belt has no noticeable affect upon the plane's velocity. All the conveyor belt does is cause the wheels to spin twice as fast as they would without the conveyor belt. Assuming the wheel's can withstand this additional speed, the plane will move forward regardless of the conveyor belt. The conveyor belt could move 100 times as fast as the plane and the plane would move forward as if the conveyor belt weren't there at all. And, since the plane is moving forward and wind is getting across the wings, it will take off, whether or not the conveyor belt is there.
Posted 21 Dec 2011 at 2:46pm #
I just saw the episode and as the myth was presented on the show, it wasn't done propery.. lets just leave it at that.
Ok if the tarp can not hold the plane stationary relative to the ground, that's a fact. But why don't they even mention this in the first place?
For me who's not a physics expert, and I guess 95% of all their viewers, the plane was supposed to be stationary and then fly off, that's how they showed the myth at first. And I thought that would be impossible on so many levels.. And when Jamie said that the myth was rediculous (or whatever he said) I couldn't agree more.
Then the plane clearly moves forward and takes off.
Conclusion: Mythbusters BUSTED!!!
Posted 21 Dec 2011 at 2:55pm #
Oh Erik, you're obviously a really cool guy who can sit behind a computer and call people names. That is so awesome and you're my hero.
Anyway, the first thing you wrote here was:
"It's not clearly evident." (that the aircraft is accelerating faster than the treadmill is being pulled.)
WHAT????
If you can't even tell if a plane on the tv is moving forward or not, you shouldn't go around calling other people stupid...
Posted 21 Dec 2011 at 3:31pm #
Martin said on December 21, 2011:
Moron (I may have misspelled your name): you are being stupid. Your own pre-conceived notions are preventing you from truly understanding the problem and, thus, from intelligently commenting on it.
Of course the plane moves forward. DUH. There's nothing which says it cannot. The only people who think that's proving something are the idiots who "read into" the problem something that isn't there.
The plane's wheels are free to rotate. The plane has a velocity related to the ground. The belt moves the same speed in the opposite direction. The wheels spin.
Nothing prevents the plane from moving forward.
Posted 21 Dec 2011 at 3:32pm #
This has got to be the BEST comment thread EVAR! So much entertainment.
And I don't even know why.
The wheels of the plane are not powered. They could be frickin' blocks of ice and the plane could still take off (barring weight issues), conveyor belt be damned.
The only way a conveyor belt could stop the plane is if the wheel bearings were so crappy that the wheels didn't move and -- and this is key -- the engine/propellor was incapable of providing sufficient thrust to overcome the friction.
Dead simple.
Posted 23 Dec 2011 at 4:13pm #
bbum said on December 21, 2011:
Oh Bill. What if the Roadrunner bought Super Duper Glue from Acme and glued the plane to the conveyor belt? Surely that would be another way.
Posted 24 Dec 2011 at 7:11am #
Martin said on December 21, 2011:
Just read the statement, as given on the Mythbusters show and website:
"An airplane cannot take off from a runway which is moving backwards (like a treadmill) at a speed equal to its normal ground speed during takeoff."
Later, they tried to make their results of their tests clearer to those less gifted among us with the following video:
http://www.youtube.com/watch?v=bEyfHwDdXSg
There are not two answers.
Posted 19 Jan 2012 (3 weeks ago) at 7:53pm #
Wow, this argument got extremely heated for no reason. I'll agree that MythBusters did a poor job explaining the myth ahead of time. They simply said "will an airplane be able to take off when it is on a conveyor belt moving backward the same speed that the plane is moving forward?" I at first thought that meant that the plane would be moving at the same speed relative to the belt, meaning that it wouldn't be moving at all relative to the ground. Obviously, if this were the case, the plane would have no chance of taking off. If it's not moving, it doesn't matter at all how much its wheels spin on a conveyor belt; it will absolutely never get the lift as no wind will go over the wings. Then in the Mythbusters video, the plane is shown moving forward relative to the ground. I then realized that this meant the plane would move at the same speed as the conveyor belt but relative to the ground. Then, it is ridiculously obvious that the plane will take off. It will still be moving forward relative to the environment at its normal takeoff speed and get all the lift it needs. Sitting on the conveyor belt does nothing because spinning wheels don't make a plane take off. My only interest in the show was that their poor explanation made me think they were going to try to make a practically stationary plane take off, leaving me angry at the end when I realized what they actually meant.
Posted 19 Jan 2012 (3 weeks ago) at 10:18pm #
Jigguh said on January 19, 2012:
Perhaps Mythbusters felt that since what you describe above is a physical impossibility, it wasn't necessary to explain it further. They evidently over-estimated the average persons' knowledge of aerodynamics. Come to think of it, I've met pilots who, when I described the myth, thought the plane would not take off. Scary!!!
Posted 19 Jan 2012 (3 weeks ago) at 10:25pm #
bbum said on December 21, 2011:
Actually, this wouldn't "stop" the plane. The plane would be moving backwards on the belt.