Will it take off?

The conveyer belt is a red herring.

Aircraft gain thrust by moving air, either prop (chopping through air) or jet (shoving hot gas out the back). Their wheelspeed is irrelevant.

The treadmill isn't capable of matching the wheelspeed of the aircraft at any time because of this.

If the plane is travelling at 100mph on the treadmill then the treadmill moves 100mph in the opposite direction the wheels will be moving at 200mph since the aircraft is still supplying thrust through the air to keep itself moving.

If the aircraft didn't take off in this scenario then no powered airoplane would ever take off on an eastward pointing runway since the earth is turning and acting like a giant treadmill.
 
lepster74 said:
If the plane is travelling at 100mph on the treadmill then the treadmill moves 100mph in the opposite direction the wheels will be moving at 200mph since the aircraft is still supplying thrust through the air to keep itself moving.
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But if the plane is moving slower than the belt? i.e. belt at 100mph and the plane at 60 mph! What is the force that would increase the speed of the wheels and why? The plane can't spin it's wheels faster than the belt :D
 
Splog said:
But if the plane is moving slower than the belt? i.e. belt at 100mph and the plane at 60 mph! What is the force that would increase the speed of the wheels and why? The plane can't spin it's wheels faster than the belt :D
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If the plane is travelling at 60mph then the wheels would be going at 160mph. Remember the wheels on an aircraft provide no power to move an aircraft, they basically a more robust version of a front wheel on a bicycle so whatever the treadmill does the wheels will just turn and have no effect on the plane.
 
Splog said:
But if the plane is moving slower than the belt? i.e. belt at 100mph and the plane at 60 mph! What is the force that would increase the speed of the wheels and why? The plane can't spin it's wheels faster than the belt :D
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It can, although not under the experimental conditions you have specified.

You still haven't explained how the plane can move under your experimental conditions. Until you explain that all further discussion is redundant.
 
I've seen this question actually kill a forum before now, so much was the heat that built up in the discussion. Haven't read past page one but I hope everyone is being chilled.

The answer, of course, is yes. :)
 
onomatopoeia said:
It can, although not under the experimental conditions you have specified.

You still haven't explained how the plane can move under your experimental conditions.
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But where would be the fun in that! ;)

Consider a wheeled aircraft on a very slippery ice runway? How fast do the wheels need to turn to allow the aircraft to take off? What would happen to the take off if the pilot applied the (wheel) brakes? Now consider how the backward running belt (if it is actually running backwards!) will affect the drag on the wheels? if the belt is at the same speed or greater than that of the forward motion of the plane? :D

dazzajl said:
I've seen this question actually kill a forum before now, so much was the heat that built up in the discussion. Haven't read past page one but I hope everyone is being chilled.

The answer, of course, is yes. :)
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But what was the question? ;)

photon said:
You, Sir, may have just killed this forum! ;)
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Nah! Everyone's playing nicely ... :cool:
 
Is this the same as shooting a Harrier of the back of an aircraft carrier going backwards? :thinking:
 
Splog said:
But where would be the fun in that! ;)
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Where would be the point in continuing if you don't?

Certainly no point in considering your analogies, it's the defined experimental conditions that are the only relevant things.

You have stated that certain things happen. Some of these things contradict each other. You have refused to explain how the contradiction is overcome.
 
onomatopoeia said:
Where would be the point in continuing if you don't?

Certainly no point in considering your analogies, it's the defined experimental conditions that are the only relevant things.

You have stated that certain things happen. Some of these things contradict each other. You have refused to explain how the contradiction is overcome.
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OK, Put it this way :) Why does it matter what speed the belt is turning (assuming opposite direction) ? The wheels and the belt are interacting with each other and definitely not the plane! If the wheels were retarded by the belt this would induce a breaking effect, but the belt matches the wheel speed so this cannot happen (The real question is what causes the wheels to spin?)
The clarity or confusion occurs when the thinking focuses on the wheels and belt! .. The aircraft is moving through the air and not against the belt. The only interference possible with the aircraft is the axles or wheel bearings
:thinking: So providing the wheel speed matches the aircraft forward velocity (in simple terms) the aircraft can move :)

Consider the belt running backwards with the plane sat on the belt! How much force would it really take to hold back the plane so it didn't move backwards ... I would suggest very little!

To sum up:

If there is no resistance / friction in the wheel bearings or axles then whatever the wheels do (in any direction) is totally irrelevant providing they match the speed of the aircraft's motion, which they will (y)
 
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