speerchucker, you are correct that the plane takes off but not the reasons why. A jet, with engines beneath the wings and the exhaust behind the wing will also take off. A plane that does not have powerful enough engines to take a plane straight up but with enough power to accelerate to take off speed will take off. The propellers do not force enough air over the wings for the plane to take off, if that were the case a plane could hover in midair with the wings horizontal to the ground, (forget the harrier or biplanes flown slowly, tilted near vertical, with the engines running full throttle, not relevant).
It's all based on WHERE the power comes from. The engines, jets, propellers, whatever, not the wheels. No matter how fast the treadmill goes, the plane will always move forward and take off. Forget the friction of the wheels, bearings locking up, not part of the myth and not relevant to the myth. Apologies to misabear and rickbrant who I saw first use this analogy 2 or 3 years ago, (this myth has been driving us nuts for longer than that), here is an easy way to figure this out. Put on a pair of skates, tie one end of a rope to your waist and the other end to a fixed object in front of you, tree, whatever. Stand on a treadmill and crank it up. You will not move as the rope holds you in place. Now, crank up the treadmill even faster and pull yourself along the rope. No matter how fast the treadmill goes you will always go forward. The treadmill cannot hold you back. Same situation with a plane except instead of a rope, the plane is pulled through the air via the engines.

The fact that many aircraft can pull a hammerhead (flying straight up with no aid from the wings) is proof that a plane can take off with no use of its wings. If you put a helicopter on a moving conveyer would it take off? Yes it would. Even a dummy knows that! NUFF SAID. Rod What part of english are you having trouble with?

quote:

The fact that many aircraft can pull a hammerhead (flying straight up with no aid from the wings) is proof that a plane can take off with no use of its wings. If you put a helicopter on a moving conveyer would it take off? Yes it would. Even a dummy knows that! NUFF SAID. Rod What part of english are you having trouble with?

Where in the myth does it question whether or not a helicopter can take off from a treadmill? A helicopter is not a part of the myth. Being able to take off straight up is not part of the myth. Even a dummy knows that. I know why the plane takes off from the way it is stated in the myth. What part of English are you having trouble with?

Ender

quote:

You may think that is what you have said, but you obviously haven't been saying it well.

I have said the words, "relative to eachother" many times. I haven't explained it well because of the fact that I hadn't thought it through and was wrong, so any explaining wouldn't have accurately described them being in relation to eachother.

quote:

More proof that you aren't very good at saying what you think you're saying

Agreed.

quote:

Originally posted by Javaman:
I could go back and quote all the times I have said they are relative to eachother, but that would take way to long because there are way too many times.

Quote:

quote:

Originally posted by EnderGT:
Actually, please do. Even once or twice would be great.

Alright
p. 241

quote:

My point is this: if the speed of the plane and belt are in relation to eachother instead of the ground, then there is a glitch in the myth. In order for the plane to move forward in relation to the ground, then it would have to go faster than the speed of the belt (in relation to the plane) and that would go against the condition set by the myth that the belt could match speeds with the plane.

The two hang-ups that are being discussed are
1)should the speeds of the belt and plane be in relation to eachother or to the ground.
and
2)which one of these did the MythBusters believe.

Also p.241

quote:

I agree 100%. What I'm saying is that everything they said and did indicates that they believed the speeds should be in reference to eachother.

Are two on one page enough?

quote:

originally posted by EnderGT:
I agree that you have said you expected it to move once testing began. What I disagree on is that this clip states that the speeds must remain equal throughout the test. All this clip stipulates is that they start out equal, and for the plane to exceed the belt speed is AOk by that clip.

But the myth says that the belt can adjust its' speed to match the speed of the plane. That certainly seems to indicate that their speeds will match throughout the entire test.

quote:

originally posted by EnderGT:
If we were to go by the conditions required by the myth, then this clip would clearly be inaccurate, because the belt is moving while the plane is not. Since both speeds are measured relative to the ground, and since the belt must adjust and match the plane's speed, then if the plane isn't moving, the belt shouldn't be either.

But the wheels are moving relative to the belt even though the plane isn't moving relative to the ground. I'm discussing that with thespecialist so I won't say more here.

quote:

originally posted by EnderGT:
You're contradicting yourself again. You claim you're saying the Mythbusters did not believe the myth (that the plane would be held in place), just that they share Mark's interpretation that the plane will be held in place. The setup clearly has the plane moving relative to the ground as the belt moves relative to the ground. Simply start the official test at 0:01 past when the plane starts moving, and they have satisfied the wording of the myth in which the plane and belt are moving.

Either way, it makes no difference whether or not the plane is moving at the start of the test or not. The plane will accelerate and there's nothing (short of rational's infinite acceleration theory) that the conveyor can do to stop it.

No, I'm not contradicting myself. Let me put it this way: if I said, "that girl is hot," the first thing you would have to decide is whether I am saying she is a balmy 102 degrees Fahrenheit, or if I am saying that she is really good looking. You decide to interpret what I said as -she is really good looking. That doesn't mean you agree with me. You may think the girl is uglier than my dog's butt. BUT, you agree with me that the proper way to interpret what I said is that she is really good looking. In the same way, all I am saying is that the MythBusters agree with Mark's interpretation of the myth, not what he thinks the outcome of the myth will be. So, if his interpretation is that the plane will be held in place, then they also agree that the intention of the myth was for the plane to START stationary relative to the ground. But since the myth requires the plane and belt to be moving BEFORE STARTING the test, that must mean that it intends for the planes' speed to be relative to the belt.

quote:

originally posted by EnderGT
So what? Call the beginning of the test the 0:01 mark, and your starting conditions are satisfied! Once again, it doesn't matter, the plane would still take off.

The myth requires the plane and belt to be moving before the start of the test. Try passing that 0:01 stuff by a scientist. A starting point is fixed at 0:00.

quote:

originally posted by EnderGT
Yes, there is, but you rapidly filled it up by refusing to listen to counterarguments. For the record, I don't agree with him calling you a troll, but there has obviously been some miscommunication that has led to you coming across as somewhat thickheaded.

I agree. I wish I was more eloquent in expressing my thoughts because there is still some miscommunication that is happening and I will take my fair share of the blame for that.

thespecialist,

quote:

Why? Because if the rotations of the rubber-portion of the wheel are fast enough, the hub of the wheel advances - forward - against the opposite rotations of the belt...

This is exactly what I am calling the glitch in the myth. This is the end point that started this whole debate. Unfortunately, it ended up being a debate about what the speed of the plane is in relation to. I still think that there is a good argument for the speed of the plane to be in relation to the conveyor belt. Since the myth has both the plane and belt moving before the starting of the test, then the interpretation which offers the best question is for the plane to be in relation to the belt. It would, as I said, be a hypothetical situation since the planes' wheels wouldn't spin without some sort of thrust either of their own or through the belt, but the question asked in this scenario actually questions where the plane gets it's thrust. If the plane were already moving forward in relation to the ground before the testing began, that wouldn't offer much of a question. It would only be asking if the engines (regardless of where the thrust was distributed) could overcome the belt. It wouldn't call into question where the plane gets its' thrust.

Is the "glitch" your only reason for allowing the wheels have a velocity of their own?

Hasn't it already been discussed why it's not reasonable, nor scientifically sound, to take velocity of the plane via the RPM of the wheels.

Heck if you want to get technical about it, the myth never states how the plane is on the treadmill. It could be on wheels, ski's, or on its belly.

The fact remains as long as the plane's engines are powerful enough to able to over come static/rotational friction, and get to take off speed, the treadmill will still have no effect in preventing the plane from taking off.

I see no glitch in the THOUGHT experiment.

Out of curiosity Javaman, Why is this the only thread you have EVER posted on?

quote:

Originally posted by Javaman:
thespecialist,

quote:

Why? Because if the rotations of the rubber-portion of the wheel are fast enough, the hub of the wheel advances - forward - against the opposite rotations of the belt...

This is exactly what I am calling the glitch in the myth. This is the end point that started this whole debate. Unfortunately, it ended up being a debate about what the speed of the plane is in relation to. I still think that there is a good argument for the speed of the plane to be in relation to the conveyor belt. Since the myth has both the plane and belt moving before the starting of the test, then the interpretation which offers the best question is for the plane to be in relation to the belt. It would, as I said, be a hypothetical situation since the planes' wheels wouldn't spin without some sort of thrust either of their own or through the belt, but the question asked in this scenario actually questions where the plane gets it's thrust. If the plane were already moving forward in relation to the ground before the testing began, that wouldn't offer much of a question. It would only be asking if the engines (regardless of where the thrust was distributed) could overcome the belt. It wouldn't call into question where the plane gets its' thrust.

Is the "glitch" your only reason for allowing the wheels have a velocity of their own?

Yeah, and if you read my next post after that one, you can see that I obviously wanted to EDIT that post you are displaying, but couldn't due to the new nifty posting features we have here at Disco regarding editing time. My next post mentions that the wording I chose was flawed -- so too is your hanging on to it for taking it totally out of context -- like a troll would do.

quote:

Originally posted by Denie2:
"A plane on a treadmill where both the plane and treadmill are going the plane’s take-off speed (but in opposite directions)"

What seems to be so confusing here? "Both plane and treadmill (conveyor, whatever) are going AT THE PLANE'S TAKE-OFF SPEED" This means airspeed, period. This means the plane must be moving forward with an airflow over the wings sufficient enough to produce lift. Assuming there is no wind and plane is at take-off airspeed, say 60 mph (which is equal to ground speed with zero wind), then the surface of the tread is moving at 60 mph in the opposite direction. The wheels are now moving (spinning)at 120 mph (ground speed) but the plane is still at 60 airspeed. The only thing happening here is the wheels are spinning faster, in the same direction and producing an insignificant amount of additional resistance.
The plane is still moving forward at take-off speed, period.

If you think not, then answer this...
Can a plane with a 60 mph take-off speed take off with a 60 mph tail wind?

Stupid post.

The plane is NOT initially at take off speed with respect to the ground and air, if it was it would be moving with respect to the them and would be flying as an initial condition!!

The initial condition of the myth and rewordings is clearly zero airspeed.

The takeoff speed used in the mythbusters rewording clearly has to be with respect to the BELT!

Why do you have such a problem with this only moderately difficult concept? Your only defence for not understanding would appear to your stupidity.

quote:

Originally posted by Denie2:

quote:

Denise2,
If the plane is already going at take off speed at the beginning of the experiment, then what is there to test? Having a plane that is already going at take-off speed would offer no riddle. Answer this question for me. If the plane is already going at take-off speed, then what proposed force could the belt have on the plane to keep it from taking off? What do you think the myth would be questioning if the plane were already moving?

The myth states matching take-off speed. How do you propose to match take off speed if the airplane is not a take off speed?

Makes no difference anyway. You can start the conveyor first if you wish, run it up to 60 mph. The airplanes prop produces more than enough forward thrust to move the plane with it's wheels spinning (at the start) at 60 mph up to 120 mph. As I explained, the 120 mph wheel speed does not over power the thrust of the prop. A wheel spinning at 120 mph does not produce significantly more resistance than a wheel spinning at 60 mph.

Another stupid post.

If you maintain that the takeoff speed is relative to the ground it is already moving and flying!

The takeoff speed in the mythbusters rewording is clearly designed to be relative to the belt.

quote:

Originally posted by Denie2:
Java...
Here one the mythbuster website they state "MATCH SPEED". But, I don't care how you want to state it the end result is the same.

You can not stop the plane from moving forward by turning it's wheels at twice the speed (by use of the conveyor)than they would if on the actual stationary surface.

It does't matter if the plane takes off, that isn't the point. Can the conveyor stop the forward motion of the plane by matching that speed? No, it can not. No, you don't get to to speed the conveyor to Mach 1.5 in order to say it can...this would not be matching the speed of the plane

If the conveyor belt accelerated such that the plane was held stationary relative to the ground because of the forces the belt would apply to the plane, then the speed of the plane relative to the belt and the speed of the plane relative to the ground would match.

The belt could be going at 10 000 mph, for instance, and the speed of the plane and the belt would match.

You don't seem to have any understanding of the issues.

quote:

Originally posted by thespecialist1:
I think you've got it perfectly, Denie2. By the way, there has been a lot of interesting proposals that the thought problem is nothing more than a trick question - with the wording of the problem causing a sort of meaningless loop of logic that makes it impossible for the plane to be allowed to fly. I don't buy that at all. It is not a trick question. The thought problem is meant to test your ability to recognize what is relevant and what is not, that is all.

Denie2 has no grip on the issues whatsoever and seems incapable of making any intelligent comment.

There are 2 things I don't understand here:

1. They have clearly stated they will not revisit the myth, so what's with the 244 pages of bickering? If you look at the producer's post (which I'm sure many of you have) about why they got it right, it explains quite a bit (I think).
Planes of a Coveyer Belt-why we got it right by Dan Tapster, MB executive producer

2. What's with the calling each other "stupid," or people's post's "stupid?" I've come across some aggravating posts on the forum lately, but I haven't felt the need to resort to name calling. Can't one engage in intellectual debate without lowering themselves to that level?

Thanks just my two cents ::ducks in case of flaming::

Caitlin

quote:

Originally posted by roofingguy:

Actually it has been discussed many times and a free-rolling wheel has no friction at all between itself and the surface it's rolling on... it only has some rolling resistance. The actual friction only comes into play when the wheel is driven or used for braking, and is not free-rolling.

For all intents and purposes, the friction between the plane's wheels and the belt (or any other runway) is zero.

Roofingguy, these statements are erroneous.

There are considerable frictional forces between the wheel and the belt! These forces cause the wheel to turn!

I think you probably meant that there are in effect no frictional forces acting on the body of the aeroplane, which is quite different to the wheels.

quote:

Originally posted by -rational-:
Denie2 has no grip on the issues whatsoever and seems incapable of making any intelligent comment.

Well, for the one post that I read of his, it made more sense than javaman's did at the time.

Speeds here are measured relative to observer -- the sensor which is one observer and the point of view of the writer of the thought problem which is the other observer -- AND they are both at the same velocity throughout. (see below)

The ground, conveyor machinery, all other things either stay at the same velocity of the observer or change their velocities depending.

The observer is apparently set motionless upon the Earth. That velocity has a number of things attached to it which have no bearing on this thought problem, however, help to further define the observer's velocity. Though motionless, they (sensor and observer) have the acceleration due to gravity acting upon them, they turn with the rotation of the Earth. They travel with the Earth in the Earth's orbit and also track along with the solar system and other such things. HOWEVER, since so too do ALL the other things in this thought problem, all of that cancels out and we are left with a motionless set of observers relatively speaking(sensor and observer) while the greater part of the machinery of the conveyor, the ground and wind also remain at the same velocity through out. While everything else moves dependent upon the motions of the plane and not the rolling surfaces of the wheels: (belt, plane -- direct airflow over skin of plane supplied by propeller -- relative airflow over wings created as the plane and wings push through ambient stagnent air -- all relative to observer)

quote:

Originally posted by -rational-:
The takeoff speed used in the mythbusters rewording clearly has to be with respect to the BELT!

I disagree with "clearly". I do think they reworded it badly, and that it more strongly suggests that it is relative to the belt than that it is relative to the ground, but there is enough wiggle room that it is not "clearly".

I also agree that, if you measure the speed of the plane relative to the belt, then your proposed theoretical infinite acceleration scenario is capable of preventing the motion of the plane.

I hope you agree, though, that if you measure both speeds relative to the ground, then the belt has very little effect on the plane's ability to move and thus take off.

Didn't we just go over this with that other guy?

You cannot have the belt speed be the reference without invalidating the original question.

Also I never saw where MB specifically mentioned that velocities is relative to the belt.

quote:

Originally posted by thespecialist1:

quote:

Originally posted by -rational-:
Denie2 has no grip on the issues whatsoever and seems incapable of making any intelligent comment.

Well, for the one post that I read of his, it made more sense than javaman's did at the time.

Speeds here are measured relative to observer -- the sensor which is one observer and the point of view of the writer of the thought problem which is the other observer -- AND they are both at the same velocity throughout. (see below)

The ground, conveyor machinery, all other things either stay at the same velocity of the observer or change their velocities depending.

The observer is apparently set motionless upon the Earth. That velocity has a number of things attached to it which have no bearing on this thought problem, however, help to further define the observer's velocity. Though motionless, they (sensor and observer) have the acceleration due to gravity acting upon them, they turn with the rotation of the Earth. They travel with the Earth in the Earth's orbit and also track along with the solar system and other such things. HOWEVER, since so too do ALL the other things in this thought problem, all of that cancels out and we are left with a motionless set of observers relatively speaking(sensor and observer) while the greater part of the machinery of the conveyor, the ground and wind also remain at the same velocity through out. While everything else moves dependent upon the motions of the plane and not the rolling surfaces of the wheels: (belt, plane -- direct airflow over skin of plane supplied by propeller -- relative airflow over wings created as the plane and wings push through ambient stagnent air -- all relative to observer)

Nope, wrong.

If I asked you to measure the speeds of the winds on Jupiter what would you make those speeds relative to? If I asked you how quickly a person was running on an aeroplane, what would say his speed was relative to?

The sensible answers are NOT relative to some observer planted on the surface of the earth.

It is perfectly normal to ask questions in which a speed measured in one reference frame is used in another, so for instance to run on the ground at the same speed as someone running in an aeroplane or on a boat or whatever. This is a perfectly normal engineering and scientific technique.

This idea of movement being measured to some universal observer are not implied in the myth and this idea has no relevance to it.

So measuring the speed of the aeroplane relative to the belt and having a control system which sets the speed of the belt relative to the ground is a perfectly reasonable interpretation of the myth. In fact it is the only sensible interpretation for the myth to offer any well defined intellectual challenge.

If the speed of the aeroplane were measured relative to the ground then a car in place of the aeroplane in this myth would move relative to the ground at half the speed that appears on the speedometer as established in many posts e.g. if a car can do 120mph relative to the belt it would do 60mph relative to the ground. If the car had wings and its take off speed was 60mph, it could take off, and such cars with wings do exist. This myth does not represent much of a challenge if a car with wings could take off.

The obvious intention of the myth wording was to suggest that there was some possibility that the conveyor could prevent the aeroplane from moving relative to the ground, just as a human or a car would be prevented from moving relative to the ground.

Many people have suggested that having the speed relative to the belt leads to a mathematical contradiction when the aeroplane moves relative to the ground, because of course once the aeroplane moves relative to the ground the belt cannot match the speed of aeroplane relative to the belt even if the belt were to go to infinite speeds because the following has to be satisfied
( this equation has been derived repeatedly)

Vb = Vb - Vpg

Vb = Velocity of belt
Vpg = Velocity of plane relative to the ground

But this does not matter!!! Because once the plane begins to move relative to the ground its take off is inevitable as it is capable of accelerating, and in fact the myth could effectively ask the question at the end "Does the plane accelerate and eventually take off?" and once the plane does accelerate the myth is answered and the control system which governs the belt speed has failed to keep it in place.

People may argue that by measuring the speed of the plane relative to the belt that the myth condition which states the belt "matches its speed" is broken. But as I said above the break occurs because the plane accelerates and effectively answers the myth, but additionally this condition is broken in the real world even if the speed of the plane is measured relative to the ground. The speed of the belt never matches the speed of the aeroplane if it accelerates. As the aeroplane accelerates there MUST be a lag in the acceleration of the belt, unless one assumes non-real world fictional physics, and so the belt never "matches" the speed of the aeroplane at any time it is accelerating. The belt speed might be close but it will NOT match if the plane is accelerating. So the myth conditions are broken in ALL cases.

The myth would be best worded by saying that the control system "tries to match the speed of the aeroplane" and that is perfectly compatible with measuring the speed of the plane relative to the belt.

quote:

Originally posted by saintj858:
Didn't we just go over this with that other guy?

You cannot have the belt speed be the reference without invalidating the original question.

Also I never saw where MB specifically mentioned that velocities is relative to the belt.

See my post above to answer your points.

quote:

Originally posted by EnderGT:

quote:

Originally posted by -rational-:
The takeoff speed used in the mythbusters rewording clearly has to be with respect to the BELT!

I disagree with "clearly". I do think they reworded it badly, and that it more strongly suggests that it is relative to the belt than that it is relative to the ground, but there is enough wiggle room that it is not "clearly".

I also agree that, if you measure the speed of the plane relative to the belt, then your proposed theoretical infinite acceleration scenario is capable of preventing the motion of the plane.

I hope you agree, though, that if you measure both speeds relative to the ground, then the belt has very little effect on the plane's ability to move and thus take off.

I not only agree that if both speeds are measured relative to the ground that an aeroplane would have no problem taking off, but that a car fitted with wings and which was capable of 120mph on the belt and a take off speed of 60mph would also take off. Cars like this do exist in the real world.

quote:

Originally posted by caitekins:
There are 2 things I don't understand here:

1. They have clearly stated they will not revisit the myth, so what's with the 244 pages of bickering? If you look at the producer's post (which I'm sure many of you have) about why they got it right, it explains quite a bit (I think).
Planes of a Coveyer Belt-why we got it right by Dan Tapster, MB executive producer

2. What's with the calling each other "stupid," or people's post's "stupid?" I've come across some aggravating posts on the forum lately, but I haven't felt the need to resort to name calling. Can't one engage in intellectual debate without lowering themselves to that level?

Thanks just my two cents ::ducks in case of flaming::

Caitlin

If you read my post on page 140 you can see the maths behind why a plane could be stopped.

Dan does not consider issues of how the plane's speed is measured: whether it is relative to the ground or the belt.

Additionally one has to decide whether the question is for all planes. In the real world a 747 would not be able to take off from a conveyor belt because no sufficiently strong belt and motor system could be built. If one wishes to make this a thought experiment then one can define infinitely strong materials and motors and all sorts of situations not considered by Dan become relevant, such as belts which accelerate at 144ms-2 and which would hold a 747 in place.