Isnt think kinda like saying youre on a treadmill going 10mph, and you increased your speed to 15mph but the treadmill increased at the same rate, you would just stay in the same position?

I just cant see how something being pushed in attempt to gain speed can gain any speed on its wheels if the wheels speed is being matched by the platform they are rolling on. I kind of see how X's point works, but the other side of the argument seems to counteract it. This question sucks lol.

 

I agree with FLYOU .. it won't move. If the treadmil increases speed at the same rate as the wheels then you will just stay at the same spot, not creating lift.

 

THE ANSWER IS NOOOOOOOOO.... it doesnt matter how much thrust the engines make if the treadmill is compensating for the energy that the engines are putting off.. the whole purpose of having engines on the plane is to move the airplane so that with the flaps in the proper position you will gain LIFT.... lift cannot be obtained without horizontal movement or Land/Air speed if you will.AND YES the tread mill negates all horizontal movement if its ran at the same speed blah blah.. soooo..

thats it.. no it cannot fly because it has no airspeed.. do you not think they would have done this on aircraft carriers already?

 

OK, say it did work and the airplane got off the treadmill.

As soon as the wheels leave the treadmill, how fast is the airplane going? Zero MPH.

It won't work unless the wind over the wing speed equals Vs0 or greater. Vs0 = Stall speed or minimum steady flight speed in the landing configuration (assuming your in landing configuration upon takeoff).

Take a look at this image:



I'll try to make this as simple as i can...

The top of the wing is curved. The bottom of the wing is flat. The air on top of the wing is pissed off because it has to change direction and move up over top of the wing. The air on the bottom of the wing is happy because it doesn't have to do ****. The air on top of the wing wants to be happy too, so it speeds up to be joined back with his brother below the wing and thus, has to travel a greater distance.

This creates a low pressure above the wing and high pressure below the wing (the same principal that allows carburators for your motorcycles to work, also known as bernoulli's principal).

Now, here's the most important part:

HIGH PRESSURE ALWAYS MOVES TO LOW PRESSURE!

Say I punch you in the face. My fist is the high pressure. The air behind you is low pressure and your head snaps back to the low pressure area. Make sense?

Now Say you have a 500,000 pound airplane parked quietly for the night with nobody inside. All 500,000 pounds of that airplane are resting on the wheels, right?

Now say you got a couple thousand of your friends together and you all put your hands on the bottom of the wings and pushed up as hard as you can. Say you pushed so hard on the bottom of the wings, that you were able to lift the airplane off the ground. Now all 500,000 pounds of that aircraft is resting on the bottom of the wing, and not the wheels, right? That's called lift. Yes, when an airplane is flying, all 500,000 pounds of that airplane are being supported by those thin little wings (and that's at 1g, at 2g's the wings would be supporting 1,000,000 pounds. Heavy jets usually have a rating of 4g's to 6g's. Amazing isn't it?)

So back to the treadmill. If you give the engines hell and unleash 400,000 static pounds of engine thrust, the plane will move forward... but as the airplane starts to move forward, the treadmill starts to move it backwards. This means the airplane stays stationary, right? How can bernoulli's principal take effect in static air? It doesnt, and all 500,000 pounds of that airplane rest comfortably on those wheels spinning at 500 miles per hour.

Hell i'll make it even more simple. Say your running on your treadmill.

Is the wind in your eyes?

 

Where the **** are the Snakes!!!

 

Heres the problem guys. Half of you are automatically looking that the part that says "THERE IS NO WIND" and asuming that means there is no pressure to make the wings lift the aircraft then it could not possibly lift. The other half are automatically assuming that the jets are on and fully running pushing all the wind through causing it to move faster than the treadmill could go no matter what speed and causing lift because of airspeed not wheel spin. I dont think everyone has the same understanding of the complete question and thats why this thing just keeps going on.

Here is what would happen. The treadmill would turn on and the plane would fall off the back of it, destroying the plane because it would be built 300 feet high for no reason. Oh and also, treadmills are not set up to pick up speed at the same rate as whats on top of it. Thats why it would fall off the back.

HAHA. This did make me think though. Good question.

 

LOL nice job digging this up.

This is an old trick question that asks if a plane can take off with a treadmill running against it, running with it, wind against it, and wind with it all at thesame speed of the wheels.

Treadmill against- the aircraft pushes air to move, not the wheels. The aircraft still moves down the runway exactly the same as if the treadmill was not there, only this time the wheels are spinning at 2x the normal ground speed, which has nothing to do with airspeed. The wind part is there to throw you off, planes take off with no wind all day every day. The trick is that people think of treadmills as providing resistance. A treadmill can spin the wheels of the plane all day, but it will not hinder it's forward progress because the plane does not use the wheels to accelerate. The treadmill is just the sidenote.

Treadmill with - This one has a trick answer as well. As you accelerate, and the treadmill matches your wheelspeed, the plane picks up airspeed at approx. 2x the rate of the ground speed. When you take off, airspeed is normal, wheelspeed is 1/2, and treadmill speed is equal to wheelspeed. The plane will still take off the same as normal and with treadmill against, because wheelspeed has nothing to do with lift. The treadmill simply slows the rotation of the wheels by 1/2 the same as the opposite treadmill increased the wheelspeed by 2x. The point is that the wheels act completely independent of airspeed and cannot affect the takeoff one way or the other.

Wind at you - The plane will take off at approx. 1/2 of normal ground speed and in roughly half the distance, because with an equal headwind the airspeed is approx. doubled. Planes need airspeed to take off, not ground speed.

Wind behind you - This is the only case in which the plane will not take off, and also the only one that people naturally think will help. With an equal tailwind, the plane never actually has any airspeed, regardless of ground speed. With no wind across the wings, the plane simlpy drives off the end of the runway, similar to how a carrier willnot launch jetswith the wind. They always turn into it. The plane is still moving, just so is all the air around it so it never has lift.

The point of the whole thing is for you to realize that airspeed cannot be influenced by ground forces acting on a free wheel. Remember that the treadmill does not move the air, it only spins the wheels. Aircraft do not need wheels to take off, they need air, thus the theory behind water-based aircraft.

This always gets people. It's a great trivia question.

 

LIKE I SAID do you not think we would have these things on aircraft carriers top have multi plane take offs at the same time? hmm.. i seem to think so..

 

Im wondering if one of the main issues here is whether or not the treadmill is active and matches the speed the wheels try to attain as the engines start pushing the plane forward, even though it was already stated in the original question that the treadmill actively matches wheel speed. TheX's idea works if the treadmill is spinning at a constant rate and does not increase speed as the wheels do. Im sure this is obvious. But if the treadmill increases speed as the wheels try to from the force of the engines pushing on the plane, then how in the hell is the plane going to move forward and gain airspeed? It cant, and I dont know why thats so hard to understand.

It seems as though there are a lot of variables to consider here, even though the questions was pretty blatant, with one variable throwing off the entire outcome, resulting in different answers.

 

You're missing the point. Planes use air to move, not the wheels. The plane will take off just as normal by traveling down the runway gaining speed until it can fly, not taking off in place,all by use of air. The wheels can spin however fast they want, it doesn't matter unless the brakes are on. If you have a training wheel on your bike that is spinning on a treadmill, does that slow your bike down? The point of the question is to confuse generally accepted standards with actual physics. The wheels of an airplane are effectively just training wheels that let it stay upright on the ground. It uses them for absolutely nothing except balance and steering, not drive power.

To put it into perspective, imagine that you are holding a model plane on a treadmill. The wheels are spinning but it has nothing to do with whether the plane is moving or not. If you push the plane forward it still moves, just the wheels are spinning faster than they normally would. That is what happens here, the plane moves forward by utilizing the force of the engines on the surrounding air, without any concern for the wheels or which way they are spinning.

The resistance of the free-spinning wheels is nowhere near enough to counteract the forward drive force of the engines, thus the plane accelerates down the runway and takes off as usual.