Mythbusters tackles the plane/treadmill

Will the plane takeoff?

  • Yes: The plane will takeoff.

    Votes: 72 56.7%

  • No: The plane will not takeoff.

    Votes: 55 43.3%
  • Total voters
    127
The person that thought this question up is a genius. When this episode airs, it is only going to cause more debate, because they will not be able to "precisely" match wheel speed to the plane's air speed and everyone will argue the result regardless of whether it takes off or not. Most of the debaters of this are so set in their ways that regardless of proof one way or another they will never beleive they are wrong. They will just question the methods used by the people doing the experiment. If Albert Einstein were alive, he could give his opinion on it with a mile of calculations and the other half would still not believe him. This may as well be a political or religious debate in the PV forum because it will go on forever.

I need to make sure I don't subscribe to this thread so I'm not flooded with emails. And I'm not going to say what my opinion is on the subject, but I know I'm right. LOL

bob
 
INEEDAGN said:
The person that thought this question up is a genius. When this episode airs, it is only going to cause more debate, because they will not be able to "precisely" match wheel speed to the plane's air speed and everyone will argue the result regardless of whether it takes off or not. Most of the debaters of this are so set in their ways that regardless of proof one way or another they will never beleive they are wrong. They will just question the methods used by the people doing the experiment. If Albert Einstein were alive, he could give his opinion on it with a mile of calculations and the other half would still not believe him. This may as well be a political or religious debate in the PV forum because it will go on forever.

I need to make sure I don't subscribe to this thread so I'm not flooded with emails. And I'm not going to say what my opinion is on the subject, but I know I'm right. LOL

bob
Click to expand...

You are probably right! And for the record, they don't even have to match the speed of the airplane. They can double or triple the speed of the treadmill right on up to the bearing/tire failure point and the plane is still going to takeoff.
 
Pitbozz said:
Okay, guys, for the folks who don't get the treadmill is irrevelant, watch this video.

Plane vs. Treadmill Solved! with - Yahoo! Video
Click to expand...

The vid is interesting - but it neglects 1 key factor in the originally posed question:

"The conveyor is designed to exactly match the speed of the plane in the opposite direction."

Listen to the whine of the toy aircraft- in run #2, the pitch is noticeably higher as it OVERCOMES the increased speed of the treadmill- as the speed of the treadmill is static, the vid didn't further your argument. Had the speed of the treadmill increased in proportion to that of the aircraft, and the aircraft had moved forward despite that proportional increase, then you'd have something!

I'll admit when I'm wrong, but as of yet, I haven't seen much to convince me of that.
 
Yeah Im still with U too.

SouthernCal GN said:
The vid is interesting - but it neglects 1 key factor in the originally posed question:

"The conveyor is designed to exactly match the speed of the plane in the opposite direction."

Listen to the whine of the toy aircraft- in run #2, the pitch is noticeably higher as it OVERCOMES the increased speed of the treadmill- as the speed of the treadmill is static, the vid didn't further your argument. Had the speed of the treadmill increased in proportion to that of the aircraft, and the aircraft had moved forward despite that proportional increase, then you'd have something!

I'll admit when I'm wrong, but as of yet, I haven't seen much to convince me of that.
Click to expand...

That experiment is no way representitive of a commercial airliner with jet propulsion. The treadmill cannot be regulated properly, especially when the string and straw will assist in the movement of the airplane since the string is not moving in the same direction as the treadmill. Take away the string and I will admit defeat.
 
Truly all this will prove is that Brittany Spears is the most fertile drug/alcohol addicted female on Earth.....on a conveyor belt.
 
Brer Rabbit said:
That experiment is no way representitive of a commercial airliner with jet propulsion. The treadmill cannot be regulated properly, especially when the string and straw will assist in the movement of the airplane since the string is not moving in the same direction as the treadmill. Take away the string and I will admit defeat.
Click to expand...
The string was just there to keep the plane from going off the side. It had no bearing on the plane moving forward on the treadmill.
 
I can see that so far there are 9 stupid people that have voted in this poll.

Examples!!
I am going to put this in the example of a car, because i dont think any of you really see the situation that is going on here.
The treadmill is acting with a force, relevant to the speed of the car, in the opposite direction. Now, this force is acting upon the car by way of the wheels. so if the wheels roll 10ft, the conveyor moves 10ft, in equilibrium
Following so far??

NOW, listen carefully. To accurately make this a similar situation, you have to realize that the planes forward motion is provided by the movement of air. And by this, the forward propultion is 100% a seperate system from the wheels all together. This means that no matter what the wheels are doing, the motion of air through the engines will be constant, and completely seperate of the wheels.

OK, now to take a car and make the forward propultion 100% seperate from the wheels all you have to do is put ONLY the front tires on the conveyor. Now the conveyor can move at ANY SPEED, and still be equal to the FRONT wheels of the car, since the front wheels have ABSOLUTELY NO EFFECT ON PROPULTION.
So, the back wheels, that are a 100% seperate system from the front wheels, just like an airplane, will still move the car forward, as the propultion system has no effect on the front wheels in anyway.

There really is no way to put this any clearer than that, and if you cant seem to see how a plane works, you will never understand this.

On a side note, all of you that say it WILL NOT move, using your logic, the plane would have to actually move BACKWARDS.
Case in point? Put all 4 wheels of the car on the treadmill, as im sure many of you are saying this. But now, the propultion system, the back tires, would also move at the same speed as the treadmill, no longer being a seperate system.
Why would it move backward then?? Because the REAR wheels provide forward motion, and the treadmill provides the equal rearward motion. BUT the FRONT wheels provide NO forward motion, but accept the rearward motion of the treadmill through the drag of the bearings and rolling resistance of the rubber.


SO HERE IS MY POINT: If you think the plane will not move, you are wrong either way. It will either take off, or it will go backwards. Use any logic you want, those are the only 2 possibilities, it cannot remain stationary.
Gary
 
What would happen if the airplane wheel are locked to the axle and cannot turn? The force of the engine would eventually push the plane and cause the wheel to skid. If the engines could build up enough speed the plane would still take off when the tires smoking.

The plane will fly. Once people open there eyes they see how illy they were being and finally agree that it will fly. Like a light bulb going off in their brain they will eventually see the light and smile.
 
SouthernCal GN said:
The vid is interesting - but it neglects 1 key factor in the originally posed question:

"The conveyor is designed to exactly match the speed of the plane in the opposite direction."

Listen to the whine of the toy aircraft- in run #2, the pitch is noticeably higher as it OVERCOMES the increased speed of the treadmill- as the speed of the treadmill is static, the vid didn't further your argument. Had the speed of the treadmill increased in proportion to that of the aircraft, and the aircraft had moved forward despite that proportional increase, then you'd have something!

I'll admit when I'm wrong, but as of yet, I haven't seen much to convince me of that.
Click to expand...

Would you agree that for every action there is an equal an opposite reaction? For a car, the action is the rear tires turn, the reaction is the road is pushed backwards or the car is pushed forwards however you want to look at it. Ok, now in the case of the airplane, the action is the thrust of the turbine engine against the air, "the air" not ground or runway or even treadmill. The reaction is the air is pushed backwards and or the plane is pushed forward. The treadmill can spin the wheels as fast or as slow as it can, the only thing it will accomplish is changing the speed of the planes "wheels". The planes propulsion acts against the air, not the treadmill or the ground. There is no force from the treadmill to counteract the force of the planes engine. The treadmill may exactly match the speed of the planes wheels in the opposite direction, but the only thing it will accomplish is effectively doubling the speed of the planes wheels as it moves down the runway.

Another example, a plane or rocket or space shuttle whatever you want is outside the atmosphere of the earth in a geosynchronous orbit. You speed up your ship in this orbit and the earth (treadmill) increases its speed to match you so that you are still in the same position relative to earth. If you want to take off for the moon, what are you going to do? You are going to use the exact same amount of thrust required to get you going as you would if the earth was still moving at the slower rate. The ship moves because the force is exerted on the plane or ship against space or air, not the earth or ground or treadmill. The plane WILL fly.
 
ITSNOTAGN said:
I can see that so far there are 9 stupid people that have voted in this poll.

Gary
Click to expand...

Kinda harsh, arent' ya, buckwheat? :confused: Mebbe I should call you stupid when you can't discuss the finer points of nuclear power or quantum mechanics, yes?
 
Brer Rabbit said:
How is treadmill irrelevant. It is the reason why the plane is not moving forward, right? The treadmill will accelerate in the direction that would prevent the plane from moving forward at all, the instant the treadmill cant keep up is the only point where the plane will move forward creating the wind over and under the wings necessary for lift. GOD I LOVE THIS TOPIC!
Click to expand...

Problem there is that if the plane is not moving forward, the conveyer is not moving backward. The plane moves forward (in relation to the ground around it) at 10 mph. The coveyor moves backwards at 10mph. If the plane is not moving forward, the coveyor doesn't move.

The question is meant to be somewhat generic, otherwise there would be no debate.

Another thing that can change the way you look at the question is how speed is measured. Speed on a plane is measured by wind speed. Lets say there is no wind. The plane gets up to 250mph wind speed, the conveyor gets up to 250 mph going in the opposite direction, the plane is still going 250 mph, but its wheels are going 500mph.
 
I agree thats what the guy said...

Pitbozz said:
The string was just there to keep the plane from going off the side. It had no bearing on the plane moving forward on the treadmill.
Click to expand...

However U cant argue that the string threw the straw wont create the slightest bit of resistance, which is all thats needed to start forward motion. Once it gets going it will continue to build speed. The experiment needs to have the string moving in exact reverse motion to the treadmill. Like I said lose the string and I will admit defeat.
 
Is the conveyer/treadmill matching air speed of the plane or land/wheel speed
 
tom j said:
Is the conveyer/treadmill matching air speed of the plane or land/wheel speed
Click to expand...

Doesn't matter, as it can only apply it's counter movement force to the rotation of the planes wheels. Which have no bearing on the forward movement of the plane from the force of the Props/jets.


I'm still going with my Infinte mass, singularity, we all die scenario.... :)
 
83hurstguy said:
gut your trunk and put a jet engine into it. Strap it to the chassis dyno. no matter how fast the dyno spins your wheels backwards, you'd better say a prayer that the tie down straps are strong enough or your car is going for a ride.

Put on rollerblades, and have a friend push you up the treadmill. If you have an external force acting on the system, the wheels and belt speed are irrelevant. If you have something holding you in place on the treadmill, whether the belt moves at 10, 20, or 200 mph, you aren't going anywhere.

Get the point yet? Just look at force pairs. Wheels drive a car, force vectors points backwards from the wheels, chassis dyno provides equal and opposite reacting force to keep car stationary. Airplane engines use thrust against the atmosphere to push forward... you'll need something that counteracts that to stop it...

This is only coming from somebody currently working on their MSME, so take it for what it's worth...
Click to expand...

That is exactly it. There is no correct answer because it is an impossible question. You could never match the wheel speed to the plane. The wheels are simply there to reduce friction between the plane and the ground. Just like water planes use skis for the same purpose. put a water plane with skis on a treadmill lubed with oil. same principle the treadmill and skis or wheels are irrelevant. The planes speed is determined by the thrust. If it is provided the thrust to reach 200mph, it will go 200mph. The plane would pull it self along just as it would a normal surface no matter what speed the treadmill was moving. Basically a treadmill could not keep the plane from moving forward since the planes movement is not relative to the wheel speed. The planes movement is relative to the thrust.
 
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