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About LinkBacksIs this the same as the van full of cages of birds and the birds all take off at the same time inside the cages, does the van weigh less?.
Actually, thinking about it, it has nothing to do with this
Is this the same as the van full of cages of birds and the birds all take off at the same time inside the cages, does the van weigh less?.
Actually, thinking about it, it has nothing to do with this
You owe it to yourself to click here really.Originally Posted by Blitzen
I cannot believe that everyone keeps going on and on about the wheels and the engines. its the wings that count most
It would still take off if the resistance between the plane and the water is low enough (hint: it is). The relative difference between the water and the plane would be 160 knots.
As has been said before, if the plane is stationary, it won't; if it moves, it will.
So, will it move? The thrust comes from the engines, so the plane can start to accelerate, and the wheels begin to turn. The conveyor tries to counter the wheel speed by going the other direction. This will increase the wheel speed further, but not slow the plane down (ignoring minimal friction at this point). In fact, the speed of the wheels/belt gets into a positive feedback loop as the belt tries to match the speed of wheels (but never will as the speed of the wheels = belt speed + plane speed). In theory, this will carry on until
a) the plane gains enough air speed to take off
b) the friction generated by the wheels on a what is now an extremely fast belt cancels out the thrust from the engines, therefore stopping the plane from reaching the air speed it needs to take off and no longer accelerates
c) far more likely to happen before b), the tyres explode, the plane falls onto the belt and is flung backwards off the runway....
That's my analysis of the problem.
Yes but the engines no matter how you look at it are responsible for the spinning of the wheels and if the treadmill is moving proportionately to the speed of the wheels then it means a value of 0 for everything... they all cancel each other out; the plane is going no where.
EDIT: I say we give mythbusters a ring, I'd love to see how they get a result from this brainteaser.
Last edited by Dorza; 15-12-2006 at 12:34 AM.
No, a plane on ice with it's brakes locked on would still take off. The wheels spinning is a clearly independant event to the velocity of the plane.Yes but the engines no matter how you look at it are responsible for the spinning of the wheels. If the treadmill is moving proportionately to the speed of the wheels then it means a value of 0... they cancel each other out; the plane is going no where
I agree, there is no upwards vector without winds hitting wings. Unless the plane is equipped with harrier type of engine, I don't think it will fly.
notsobig, thankyou... you have hit the nail on the head.
With all the respect in the world, ice is a totally different matter, theres nothing pushing in the opposite direction to the plane so the plane would lift off. In this scenario we have a treadmill which matches the speed of the wheels and therefor the plane which has a direct impact on the air moving over the wings. Unless the jets are given more power to push the plane to eventually overcome the treadmill then the plane won't take off.
Why doesn't someone do this on a smaller scale. Then you can end the debate?...
From an ilogical persons point of view (yours truly) it seems that it won't take off, as its technically stationary, which means that there is no wind, which is the requirement of lift off.
What notsobig and mart say
¯\_(ツ)_/¯
In my opinion it cant possibly take off.
Forget about the wheels, they really arent important. A plane normally needs around 160mph of airflow over the wings before it gives a positive lift. As lift is a function of air speed, density and cross sectional area the only thing that can change drastically is the velocity. The thing that propels the plane forward is the jet thrust (creating a greater opposing force to friction/gravity which holds the plane still) hence moving it forward. This keeps the plane moving forward until the amount of upward force or lift is greater than that of the planes mass*gravity.
However, if the plane is on a treadmill with the jets at full thrust it would move forward (unless the treadmill was simply frictionless), only to fall of the end onto its nose and scraping along the floor.
Thats my 2 cents worth,
Having given a bit more thought (and reading the replies), it depends how realistic you want to be (well, as realistic as getting a runway sized conveyor belt...). It comes down to this: Are the wheels frictionless?
Yes: - Then no matter how fast the treadmill goes, it won't affect the air speed velocity of the plane and it will take off as normal.
No: - In which case, how fast does the belt accelerate to match the wheel speed? If it is immediate and the wheels generate friction, then as I mentioned before, it will cancel out the thrust and keep the plane stationary. If it doesn't accelerate as quickly as the plane's air speed velocity, then there's a chance the plane can take off before the friction is too great.
lol I've seen this thread on so many forums now.
The plane will take off.
The engines aren't connected in any way to the wheels, the wheels will rotate freely in any direction and it will not make a shred of difference to the thrust and eventual take-off of the plane.
Even taking into account the slight amount of friction of the wheel rubber on tarmac, the thrust of the engines would overcome it easily. In fact, it would take off even if the brakes were on.
by redefining "take off" to a more conventional, move in the upwards direction, theoretically, theres nothing stopping it from taking off. But when the wheels leave the ground, you're going from 0mph linearly to the speed required to lift the plane, linearly. I think you'd fall out the sky
If a plane could take off from a treadmill then why do they take a 'run up' to take off. They do need to be moving as said in previous replies...follow the link below:
http://pogue.blogs.nytimes.com/2006/...ill-conundrum/
Does the plane take off? Of course it bloody does. But another forum I post on have been posting for pages and pages arguing both ways. In fact here's a 443 page (and counting) thread on a physics forum on the same subject that has been going over a year:
http://forum.physorg.com/index.php?showtopic=2417
Answers below please
Plane engines push against the air not the tarmac (or treadmill), thus it takes off. Simple really.
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