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Will this plane fly??

JeffreyDahmer said:
^ ...at exactly the same speed. That's rather an important omission.

I now understand where my own confusion arises. If the plane does not move forward (because of the equal speed but opposite motion of the plane and the belt) the plane cannot possibly take off.

If the plane is able to move forward at a fast enough speed to allow the wing to create lift, it can surely take off.

In all my visions of the problem so far, the plane has not moved forward. Now i see this problem as analogous to the runner on the treadmill. If the runner runs faster (the plane speeds up) the treadmill runs faster in the opposite direction to keep the runner in the same position (say, relative to somebody standing next to the treadmill).


Replace the runner with the plane and there is no movement forward. No movement forward means no airflow over the wing. The plane can not take off.
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There is movement forward. Your runner on a treadmill argument isn't good. Look at my rollerblader on a treadmill argument, which i have stated probably 7 times. That is what is really happening.
 
KemicalBurn said:
The plane wont take off because you guys are relying on 'zero friction'.
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Cosmic Gay-

But the plane did take off!! Have you not read anything in this thread, and/or the link i posted twice. I'm not relying on zero friction, I'm relying on the fact the the force the propeller in one way is more than the force of friction in the other. Are you really a physics major? how long has it been since you took classes? You seem to have forgotten how things move.
 
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MazDan said:
If the plane has wheels then the answer is NO. (Actually to be more precise the question cannot have an answer.......its a bit like the chicken and the egg)

Reason. There IS a relationship between the wheels of the plane and the conveyor belt. Anytime the plane moves forward (lets say one rotation of the wheels) the conveyor belt must move backwards by an identical ammount.
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Are you telling me, that if you are on a conveyor belt with roller blades(say a 20 ft conveyor belt), you couldn't use the rails to move up the conveyor belt?

You could, assuming you generated enough force on the rails to overcome the force of the friction moving you backwards.

(i've done this once before)

<========== pull on the rails
{you on conveyor belt}
=============>friction caused by conveyor built going backwards(due to gravity)

if one force is more than another, you will go that way. basic physics.
 
bGIveNs33 said:
There is movement forward. Your runner on a treadmill argument isn't good. Look at my rollerblader on a treadmill argument, which i have stated probably 7 times. That is what is really happening.
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your rollerblade argument was flawed. ive stated previously why.
 
I think the trolley on the Heathrow travelator illustrated it fairly well. If you're not willing to accept that as logic I don't see a point in continuing the debate. The answer has been indicated time and time again.
 
KemicalBurn said:
This simply isnt the case. Your rollerblade/treadmill analogy is weak - here's why:

*the conveyor belt moves in the opposite direction of the plane and at exact the same speed.

*your analogy doesnt take into account that if the pilot were to get out and push (which is the basis of your analogy) you arent taking into account that the conveyor belt will counter-act this by speeding up. which has already been stated that it will.
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A pilot getting out and pushing is ridicolous, because he would be on the treadmill, dealing with that same friction. That is NOT the same thing. If he were to tie to ropes to it(on either side) and pull it forward from a source of the conveyor belt, now that is the same thing. Again, this is basic physics, the force from the propeller is greater that the force of the friction. That is all that is going on. Very Very basic.
 
AN didnt account friction.

and the article/experiment would not be able to perfectly replicate the circumstances required by the original question.
 
I am sure this thread will still be going round in circles if it was on page 693, not page 4.
 
nice sig sickpuppy........ but it's obivious you read the question and skipped the rest of the thread :)
 
bGIveNs33 said:
A pilot getting out and pushing is ridicolous, because he would be on the treadmill, dealing with that same friction. That is NOT the same thing. If he were to tie to ropes to it(on either side) and pull it forward from a source of the conveyor belt, now that is the same thing. Again, this is basic physics, the force from the propeller is greater that the force of the friction. That is all that is going on. Very Very basic.
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so now the original question isnt whether it will fly, but how you can make it fly?
 
bGIveNs33 said:
nice sig sickpuppy........ but it's obivious you read the question and skipped the rest of the thread :)
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Yeah.I'm bad about that.I got add i think.
 
i think alot of you are confusing physics with aerodynamics with out lift the plane can apply all the power it wants it will not fly .



by your arguement would the plane would fly if it was tethered to a pole?
 
johnnyb420 said:
i think alot of you are confusing physics with aerodynamics with out lift the plane can apply all the power it wants it will not fly .



by your arguement would the plane would fly if it was tethered to a pole?
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It certainly will fly because it is moving. The fact that it is moving will allow it to create lift.
 
OK I have finally solved this one.

Yes the plane CAN fly even if it has wheels.

It was the wheels that were throwing me and the fact that they have to make an equal movement with each movement of the belt hence there is no slip anywhere to allow the plane to move ahead.

But while that is true.........I had forgotten about the slip that occurs between the axle and the wheels...........THAT is where the slip happens.

What made me think was that if I put a plane or roller blades or anythinbg with wheels down on a length of paper and pulled that paper........the plane or blades would stay still.........why?.........because the movement or part where the fricftion would occur was at the axle.

For a plane with skids the friction point is at the skids.

It all makes perfect sense now...........finally..........lol.

Thanks to all for your patience with me.

Hope that explanation will help some others also.
 
-T{H}R- said:
It certainly will fly because it is moving. The fact that it is moving will allow it to create lift.
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in the original question it says the plane does not move\




"On a day with absolutely calm wind, a plane is standing on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. The conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). Can the airplane ever take off?"
 
Sure, it is standing until it starts to move for fucks sake. It does not say it does not or cannot move.
 
it says that movement in one direction is conteracted in the other direction in my calclation that means it does not move,of if it reaches liftoff speed in the forward direction it will takeoff the qestion is not if it can overcome this imaginary conveyer the way the question is parced it does not move
 
KemicalBurn said:
AN didnt account friction.
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But aren't you assuming a conveyor belt which can respond instantly and perfectly to the plane? Both cases are idealised. If you accept the existance of such a perfect conveyor belt (which itself must have zero mass or experience infinite force, or else it's reactions cannot be instant) then you accept no friction.
johnnyb420 said:
it says that movement in one direction is conteracted in the other direction in my calclation that means it does not move,of if it reaches liftoff speed in the forward direction it will takeoff the qestion is not if it can overcome this imaginary conveyer the way the question is parced it does not move
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You're running on a treadmill, and no matter how fast you run, the treadmill keeps you in the same place. Your friend walks round to the front of the treadmill, sticks his arm out, you grab it and he yanks you off the the treadmill against the flow of the treadmill. By having an additional force which isn't having to act against the treadmill, you can easily overcome it. Same goes for the "yank" the engines give the plane.

As MazDan has pointed out, it is better to think of it, not with wheels but skids. If the skids have no friction between them and the conveyor belt, the belt can move as fast or as complicated as it likes, no momentum will be imparted onto the plane. From the planes point of view, it cannot tell if the ground is moving or is still. Hence when it started up it's engines it would accelerate and take off as normal.
 
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