Calling all clever people :) What do you make of this?

[quickshift]

Taken from another forum I use, this poser was put forward and argued with incredible conviction from 5 angles or more, to reach either of two possible answers.

It's a pretty simple question but had some brilliant rows about all sorts of things going on to justify the answers.

Imagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.

There is no wind.

Can the plane take off?

Your answers please, and please expand on them if possible

[eVITAERC]

What exactly do you mean by "speed of the wheels" and "direction of rotation"? Does this effectively mean that the plane would remain stationary from the point of refrence of the ground?

[quickshift]

The conveyer simply matches the speed of the wheels but moves in the opposite direction - there isn't any more information than that.

Whether the plane takes off or not.... That's what you have to work out

I won't add anything anyone from the other forum has posted yet

[analog_sa]

I am probably not clever at all as i can see nothing interesting about the question or answer - it seems awfully trivial and difficult to expand upon. Then again at diyaudio even the most boring and trivial topic can attract thousands of respondents

[Mr Evil]

The plane can never take off. To take off, air is required to flow over the wings to generate lift, but since the plane remains stationary with respect to the ground (if I interpret the question correctly) then, given that there is no wind, it is also stationary relative to the air = no lift.

What arguments were used in favour of it being able to take off? I cannot conceive of any sensible ones, unless I have misunderstood.

[PeteM]

Hmm

Are you saying if the plane switched off power then it would travel backwards..?

With several exceptions (harrier helicopter) an normal aircraft wing needs forward motion to generate lift.

So in short your plane would not take off.

walk against an escalator at the same speed you will appear to be stationary.

[Netlist]

If the belt rotates in opposite direction of the wheels and the speed matches, the plain stands still.
Even with no wind a plane take-off is established by the speed of the plane, generating wind or better said air pressure under the wings.
Planes should preferably take off with opposed wind or head wind to increase that effect.
So even if there was wind, it could never be enough to take off.

/Hugo

[eVITAERC]

Originally posted by quickshift
The conveyer simply matches the speed of the wheels but moves in the opposite direction - there isn't any more information than that.

Whether the plane takes off or not.... That's what you have to work out

I won't add anything anyone from the other forum has posted yet

But the "speed of the wheel" could be any of several different things! Be it angular velocity, the free tangential velocity of the wheel on its circumfrence, the velocity of the wheel surface in refrence to the fixed friction point in the negative theta direction, or the net horizontal translation speed of the entire wheel. Each one of them leads to different answers, althought I think the formulator of this question haven't quite thought this far. Similar ambiguity arises with "opposite direction". Each of those different definitions of "speed" listed above is a vector pointing in various different directions.

I think the main difficulty comes from how poorly this question is worded, not in how cleaver or decieving it is.

[quickshift]

Originally posted by eVITAERC


I think the main difficulty comes from how poorly this question is worded, not in how cleaver or decieving it is.

Indeed, it is certainly open to interpretation. Or maybe you just are free to create your own interpretation based on the mechanisms of the wheels and so on?

[eVITAERC]

Originally posted by quickshift


Indeed, it is certainly open to interpretation. Or maybe you just are free to create your own interpretation based on the mechanisms of the wheels and so on?

Any more "intrepretations" without further specification is like arguing about religion. Insofar, as such, the quesiton has no meaning.

Maybe it'll be much more fruitful (hard to do worse than completely useless) to post arguments from the other thread this was posted from, so we can all get a good laugh