A harmless little riddle

HEY TRACK-VOL,

The plane will NOT take off.

The problem is gravity. Read this post all the way through.

I understand what you are saying, but b/c of gravity, the plane MUST relay on the wheels to enable the thrust to propel the plane forward.

The treadmill CAN go just as fast as the plane's wheels...

Therefore, when the jets begin to pull the rope of air, it is nullified by the treadmill, never allowing the plane enough speed to begin lift.

Someone else said this a few pages ago, but I'll say it again. Your example of being pushed while on a treadmill is correct, but with any plane that is NOT a Harrier jet, speed must be attained before lift can be achieved.

Because the gravity is keeping the plane on the ground, it must rely on the wheels to provide speed relative to the ground before enough thrust/speed is attained for lift.

We all know the wheels don't propel the plane, you are squabbling with page 3 or 4 of this thread.

The guy above me is right, the plane's engines are not strong enough to simply throw the plane into the air.

Wheels are a necessary part of the process, sorry guys.

Why would we need runways if the plane could just take off?

If the plane doesn't take off, then it must not be moving relative to the air. In this case, the treadmill is also not moving. But then the plane will start moving...will it just jerk to a stop right away, and then go again?

There's really nothing wrong with the plane moving forward, the treadmill moving backwards, and the wheels spinning twice as fast.

http://videos.streetfire.net/player.aspx?fileid=35E964D9-38DB-4EFD-BE8D-D6BA1A43A06B

Visualize a guy on a treadmill with wheels on his feet and a jetpack on. It's not so hard to see him stationary with the treadmill going say 20MPH backwards. In this case, he would certainly move forward if the treadmill were going say 10MPH, or if he turned his jetpack up.

It's like pulling a table cloth out from under the dishes, except imagine the dishes have wheels. No friction!

To 'hey tack vol' and 'YES YES', or as I now think of you guys, "Flat Earthers"

You are both wrong.

1) The plane WILL take off

2) I have a firm understanding of gravity, and I HAVE read the thread all the way through, I suggest you do the same. Eventually, the majority of the posters realize the plane takes off.

3) The plane does NOT rely on the wheels to enable thrust, there is not power going to the wheels, the plane relies on its jet engines to propel forward through the air. The wheels spin freely.

4) The treadmill, even if it speeds up to 300 mph, will not slow the plane down, it will only cause the wheels to spin faster.

5) The treadmill can NOT nullify this, no matter how fast it speeds up to

6) We ALL agree that a plane MUST achieve speed before lift can be attained. Where we differ is the planes ability to achieve speed. The example of being pushed on a treadmill IS correct. The motorcycle/roller blade example is correct. The monkey bar example is correct. Additionally, NEW example... crank up your treadmill at home. Place a hotwheel car on the treadmill while holding it in place relative to the ground. If your treadmill is set to 8mph, than the wheels of hotwheel are now spinning at 8 mph. Now, with the hand of god (your hand) push the hotwheel further up the treadmill. You can do it right? The wheels are now spinning at 8 mph PLUS the speed you pushed the hotwheel. Even if your friend bubba, sped the treadmill up to 80 mph, you are still able to push the hotwheel further up the treadmill, it's speed relative to air will be whatever force you pushed it with, it's wheels will spin at THAT speed Plus the 80 mph the treadmill was acceleraded to. That is what the plane's engines do. There is no power to wheels, (plane's or hotwheels) only power to the outside force (jet engines pulling against air, you pushing with your own hand)

7) again the plane does NOT rely on it's wheels to provide speed on the ground, it is not a flying car, if it were a car, even a flying car with wings, then and ONLY then would you be right. The plane relies on jet engine to move it, not the wheels, the wheels just keep the fuselage from scraping the ground.

8) The treadmill can't stop the plane. How does the treadmill exert force on the plane? It doesn't. It will just make the wheels spin faster, not keep the plane from moving forward. Malmo has said so, the airplane people in their thread have said so, most every *inteligent* poster has said so. The rest of you still thing the earth is flat.

9) I don't think anyone has said that the plane's engines would just 'throw' the plane into the air. The plane will slowly begin to move forward, building speed, relative to both air and ground, and eventually take off. The wheels will be *spinning* twice as fast as the plane is traveling just before take off because the treadmill is going in the opposite direction.

10) wheels are NOT a necessary part of the process, just like a plane that lands on ice, or water. No wheels, and no boat propeler either.

11) to answer your final question of "why would we need runways if a plane could just take off" shows that you still can't grasp that the plane will travel forward, NOT stay in place 'treading water' on the treadmill like a runner or car would. Plane can't 'just take off', they need air traveling over/under the wings. In the riddles scenario, this would happen, because the plane would move through the air, the treadmill has a negligible effect on the planes movements, just the wheels.

track-vol wrote:

most every *inteligent* poster has said so.

That was morbid.

first off, if you're going to hold to one opinion without legitimately considering the other viewpoint, please don't post. this thread isn't about educating the other idiots; it's about discussing a (sort of) physics problem. on that line, don't call the opposing viewpoint idiotic.

another thing: don't argue this by analogy. a plane is not a person running, nor a car driving, nor even a roller blader being pulled by a car. regardless of whether these analogies apply, you're just replacing the word "plane" by "roller blader."

here's a good idea from an outside website. how about if instead of matching the plane's velocity we just set the treadmill at 500MPH backwards. if the plane couldn't take off with the treadmill matching the plane's velocity, then it won't take off if the treadmill exceeds the plane's velocity.

now at first, the plane will be moving backwards very fast at 500MPH. it applies it's engines, and begins to increase its forward velocity, eventually coming to a stop (airspeed), and then reaching 500MPH (airspeed). At this point, the conditions of the problem are met--the treadmill speed matches the plane's airspeed. but now, moving 500MPH, the plane is moving.

Wow...I can't believe that one riddle has led to all of this. I'm am SOOOO glad that I am a accounting major. All I will ever have to do is sit on the plane and allow the rest of you to argue how to move it...enjoy.

The plane will fly, Chuck Norris will be your pilot, and Jason Rexing your co-pilot

YES YES wrote:

The guy above me is right, the plane's engines are not strong enough to simply throw the plane into the air.

Wheels are a necessary part of the process, sorry guys.

Why would we need runways if the plane could just take off?

What's up? Never see a flying boat? Takes off from water...

What about planes that land and take off from ice, on skis? How do they manage?

you are incorrect!

you are introducing 2 types of forces;

a sliding force (you pushing)

and

a rolling force ( the force of the engines to keep the wheels spinning on the treadmill as the treadmill spins the exact opposite)

from this scenario of course the plane will take-off...

but

we don't have 2 forces.. we have only 1 force and that's the force of the engines, that make the wheels spin against the treadmill...

Track Vol,

You are being a total ass, not to mention you must not have read the guys'/girls' posts.

I don't think they are saying the wheels are propelling the plane, but that the wheels are necessary for the plane to build speed from the thrust.

I am not stupid enought to claim I am 100% correct, but I believe that the plane would not be able to take off.

You are claiming (with your little matchbox car scenario) that the plane will continue to go on the treadmill by spinning its wheels faster due to the thrust.

The point is that the treadmill will speed up with the wheels, not the plane.

The Harrier jet is a great example, the thrust of a Harrier CAN simply push the plane without speed, this cannot.

The wheels ARE needed for the plane to move forward, it is a simple problem of friction.

Think of the treadmill as being as long as a runway.

If the treadmill constantly goes as fast as the planes wheels, how does it move forward? How does it gather speed?

"The point is that the treadmill will speed up with the wheels, not the plane."

The treadmill speeds up with the plane; it's velocity it the velocity of the plane, in the opposite direction. The wheels spin twice as fast, since the plane and the treadmill are moving.

But here's the issue. If the treadmill is moving, that means the plane is moving.

Do a quick calculation to see that the treadmill is capable of stopping the plane, but it has to accelerate significantly faster than the plane to do so; just matching the plane's velocity won't cut it.

the plane would take off if the treadmill was the length of a runway. the plane would continue to move forward while the wheels spun backwards as fast as the treadmill was moving. the wheels can spin backwards as the plane is going forwards though because the force is coming from the engines and is in no way connected to the wheels.

Thanks you, rabbit. You have correctly answered the question.

The overwhelming majority of people here who've claimed that the plane won't take off are unconsciously assuming that the plane's wheels are behaving like motorized car wheels, and that they therefore are being matched, as they apply torque, by a corresponding (and speed-nullifying) reverse spin of the treadmill wheels.

Well, even if we postulate a treadmill whose wheels are matching the speed of the plane's wheels at every moment, the plane will, if given a long enough treadmill, simply glide forward, without friction, and gain speed, and eventually take off.

Planes have wheels simply to provide a near-frictionless base along which the plane can glide and gain lift. As long as we stipulate that the plane's wheels have zero internal friction, IT MAKES ABSOLUTELY NO DIFFERENCE WHAT THE TREADMILL IS DOING. It can be moving as fast as it wants in any direction. The plane will still, on its frictionless wheels, simply accellerate forward, as though gliding along on ball bearings, and eventually take off.

There's only one possible exception to this scenario. Can you figure out what it is?

Okay, I'll tell you: if the treadmill is covered with a gooey, viscious, high-stickiness-coefficient material, like honey, this will put enough drag on the plane's wheels that takeoff might not happen.

It amazing how long this tread has gone on, especially when the correct answer and links to the correct answer stated by numerous aviation and aerospace experts has already been posted.

Think a little harder people. This exact thing happens in real life all the time. Ever heard of seaplanes? They take off against rivers or tides running opposite thier intended direction of travel every single day.

How do seaplanes get moving? Think about it. They have no wheels, they have no boat propellors - all they have in contact with the water is a pair of big floats which keep them from sinking (much the same way as a normal planes landing gear keeps it off the ground). The engines of seaplanes seem to be able to get a plane moving and airborne despite the fact that its floats are in contact with a medium which is moving opposite the intended direction of travel (and the friction (drap) forces of floats in water are orders of magnitude higher than those involved with a free spinning wheel on pavement).

If you are still not convince the plane will take off than answer this question for me - How does a seaplane, or ice plane, take off with no means of transmitting force to the ground? Hint: they are not jump jets like harriers.

to "here we go again", "high and mighty" and "argh"

It has already been established that the plane will fly, I am just trying to convince the few (mostly you 3 and a couple other) of this fact.

I'm sure you are smart people and are just struggling to get over the red herring of the treadmill. Perhaps you have just already convinced yourself that it won't fly so you don't even begin to think about how it truly is possible.

The wheels are NOT needed to move the plane, the jets move the plane.

The jets move the plane.

The jets move the plane.

NOT the wheels

NOT the wheels

NOT the wheels.

Sliding force/rolling force, the jet engines are the sliding force, NOT rolling force because the jets push the plane from air, not the wheels.

Here is a site that answers such problems

http://www.straightdope.com/columns/060203.html

The plane flies.

The aviation people in their message boards have all agreed the plane will fly (they understand how planes move):

http://www.avweb.com/news/columns/191034-1.html

The plane flies.

http://tinypic.com/jg3atd.jpg

The plane flies.

What if the treadmill constantly accelerates?

Might as well give up, track-vol. They don't get it.

The engines only push air through a small section UNDERNEATH the wing -- the section where the engine is. They don't cause air to move over the entire width of the wing and certainly not much over the top. That's the difference between pushing air and pushing the plane.

However this is stated, the plane cannot take off. The air movement caused by the engines does not produce the same lift as that caused by moving the plane through the air