Plane on a Conveyor Belt

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Plane on a Conveyor Belt

Postby EnderGT » Thu Mar 27, 2008 5:40 pm

Surely by now most of you have heard of this riddle, and possibly seen the Mythbusters episode addressing the problem. Hopefully the problem hasn't been banned from this forum entirely, and I'm not breaking some rule by posting it.

For those of you who haven't seen it before, I pose the question to you thusly:

A plane is standing on runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction). Will the plane be able to take off?


Note to those who've seen this before: this is the question as originally stated, found on the physorg forums in July of 2005 (here). I have fixed the spelling errors and slightly reworded the final line. I do not believe that my changes have substantially changed the meaning of the question.
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Postby tarek » Thu Mar 27, 2008 6:12 pm

I myself haven't heard of this one......

2 questions though ...

1. what type of plane are we talking about
2. when this belt is moving, does the plane appear to be moving in reference to an onlooker from the tower ?

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Postby EnderGT » Thu Mar 27, 2008 6:27 pm

tarek wrote:I myself haven't heard of this one......

2 questions though ...

1. what type of plane are we talking about
2. when this belt is moving, does the plane appear to be moving in reference to an onlooker from the tower ?

tarek


1. Assume a typical airplane that you might see at any modern civilian airport. One or more engines, wings, stabilizers, tail, wheels, windows, etc. Assume that it's in good working order and would be able to take off normally on a fixed runway.

2. That's the question, isn't it?
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Postby tarek » Thu Mar 27, 2008 6:44 pm

EnderGT wrote:2. That's the question, isn't it?

So no easy giveaways:D

One final question as I have no idea how planes are made:

can the plane & wheels move independently?

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Postby EnderGT » Thu Mar 27, 2008 6:53 pm

tarek wrote:
EnderGT wrote:2. That's the question, isn't it?

So no easy giveaways:D

One final question as I have no idea how planes are made:

can the plane & wheels move independently?

tarek


The wheels of a plane are usually mounted on an assembly referred to as "gear". This assembly can be retractable, meaning that the wheels get pulled up and tucked into the body of the plane for streamlining, or fixed, meaning that they remain in place. The wheel itself is usually attached to the gear via a bearing that allows the wheel to spin freely.

A plane will not take off and leave its wheels behind. While the wheels are extended, the position of the wheel relative to the body of the plane is constant, and so the wheel moves with the plane.

I hope this answers your question...
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Postby tarek » Thu Mar 27, 2008 7:05 pm

EnderGT wrote:allows the wheel to spin freely.
:idea::idea::idea:
That is the answer to the riddle EnderGT, it has been a while since the grey matter was foced into action .... I have to thank you for that:D

The idea behind the wheel is support rather than propulsion
wikipedia, on Fixed-wing aircraft wrote:Landing gear: a set of wheels, skids, or floats that support the aircraft while it is on the surface.


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Postby EnderGT » Thu Mar 27, 2008 7:16 pm

tarek wrote:
EnderGT wrote:allows the wheel to spin freely.
:idea::idea::idea:
That is the answer to the riddle EnderGT, it has been a while since the grey matter was foced into action .... I have to thank you for that:D

The idea behind the wheel is support rather than propulsion
wikipedia, on Fixed-wing aircraft wrote:Landing gear: a set of wheels, skids, or floats that support the aircraft while it is on the surface.


tarek


I think you've got it, but just to be sure...

Does it fly or not?
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Postby tarek » Thu Mar 27, 2008 7:25 pm

EnderGT wrote:I think you've got it, but just to be sure...
Does it fly or not?

Yes it does. (final answer)

before your answers to my query, I was thinking of something else completely (How to make the aeroplane fly when it shouldn't)

My chain of thoughts went through :
1. tilting the engines
2. deflating the rear wheels
3. havey load on the tail .. etc

luckily, the correct chain of thinking came out when I focused on the wheels.

Thanx again EnderGT

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Postby EnderGT » Thu Mar 27, 2008 7:27 pm

tarek wrote:
EnderGT wrote:I think you've got it, but just to be sure...
Does it fly or not?

Yes it does. (final answer)

Thanx again EnderGT


My pleasure. I've been fascinated by the responses to this question, and since most are negative, it's interesting to see someone think it through and come to the correct answer on their first try.
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Postby tarek » Thu Mar 27, 2008 7:37 pm

EnderGT wrote:it's interesting to see someone think it through and come to the correct answer on their first try.

You should have been here when the off-topic section was full of riddles every day .... you would have liked it.

Lateral thinking all the way & all day:D

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Postby Bigtone53 » Thu Mar 27, 2008 10:49 pm

OK, got it. If the plane is moving forward, then regardless if what is happening below, it can take off. Nice one!

I agree with Tarek that in the past, this was an interesting area for riddles and other stuff. At the risk of being tedious, I mention again a (to my mind) pleasant question which attracted no comments before, here
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