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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Hobbess
(Post 5555455)
Has anyone questioned why the plane is even on a treadmill? Surely if it's in Canada (and why wouldn't it be as this is a Canadian forum) then it's probably a reasonably healthy plane and there are lots of nice wide open spaces to go out for a run that the use of a treadmill becomes a moot point...
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Andthen
(Post 5555471)
Hve you seen the number of fat people over here?
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Hobbess
(Post 5555474)
you are living in Canada not America?
Hell, since moving here Ive become one of the millions of fat canadians. But Im probably wrong...have been about everything else this thread has touched on it seems:) |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by iaink
(Post 5555490)
There is no difference. Are you a canadian by any chance? Only Canadians dont recognise the fact that Canada and the US are 90% interchangable.
Hell, since moving here Ive become one of the millions of fat canadians. But Im probably wrong...have been about everything else this thread has touched on it seems:) I'm sure you'd find it much easier to return the favour. |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by iaink
(Post 5555490)
There is no difference. Are you a canadian by any chance? Only Canadians dont recognise the fact that Canada and the US are 90% interchangable.
Hell, since moving here Ive become one of the millions of fat canadians. But Im probably wrong...have been about everything else this thread has touched on it seems:) Recent trip to Florida highlighted the difference. Maybe it's just a West Coast thing, what with the mountains and stuff that keeps the pounds off. Anyway back to the treadmill or lack of it, the point is that the space around in Canada means why would you get on a treadmill when you could go out for that run in the space?!? |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Hobbess
(Post 5555474)
you are living in Canada not America?
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Hobbess
(Post 5555515)
Recent trip to Florida highlighted the difference. Maybe it's just a West Coast thing, what with the mountains and stuff that keeps the pounds off. Half those fat 'mercans were probably Canadian. |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Bill_S
(Post 5555402)
OK, since we've got round to Newton, I'll have another go...
3rd Law means for every action, equal and opposite reaction. We have an aircraft stationary wrt the air around it. The action = application of thrust to the airframe. The reaction = the aircraft moves. The magic treadmill can spin the aircraft's wheels forward, backward, fast, slow... it doesn't matter what the wheels are doing. If a force is applied to the aircraft, the aircraft MUST move. Spinning the wheels CANNOT stop the aircraft from moving. (Unless the force applied is very tiny and not greater than the friction from the bearings, but that's hardly what we're talking about here). This has really got me gripped!! I started with the assumption that the magic treadmill is frictionless, and acts only in reaction to the rotation of the plane's wheels. No consideration of inertia or friction losses. Until gravity is overcome by lift, all the thrust forces are routed through the landing gear and the wheels. As the wheels attempt to rotate forward, the magic treadmill rotates backwards, resulting in zero forward movement. As thrust increases, the wheels and treadmill accelerate up to ludicrous speads, way more than take off speed, but still, there should be no forward motion. Gravity ensures that the thrust forces go through the wheel/treadmill. As long as the treadmill reacts instantaneously with the rotating moments of the wheels, there cannot be forward motion. The original poster stated that the the conveyor is "designed to match the speed of the plane exactly". On that assumption alone, surely the plane cannot move? This is fun - just like Johnny Ball's science programmes! |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by Jingsamichty
(Post 5555698)
Until gravity is overcome by lift, all the thrust forces are routed through the landing gear and the wheels. ! Ah, but they arent, the thrust acts on the airframe, pushing it along horizontally, relative to the air. Whether the wheels move or not is neither here or there, the wheels are free to rotate independent of the air frame (the brakes are off), and the plane is moving relative to the air, which is all that matters. What the treadmill is doing is of no consequence once the initial friction of the wheel bearings is overcome and the wheels start to rotate. As the wheels attempt to rotate forward, the magic treadmill rotates backwards, resulting in zero forward movement. As thrust increases, the wheels and treadmill accelerate up to ludicrous speads, way more than take off speed, but still, there should be no forward motion. Gravity ensures that the thrust forces go through the wheel/treadmill. As long as the treadmill reacts instantaneously with the rotating moments of the wheels, there cannot be forward motion. The original poster stated that the the conveyor is "designed to match the speed of the plane exactly". On that assumption alone, surely the plane cannot move? This is fun - just like Johnny Ball's science programmes As you can see I have jumped ship here and am now in the it'll take off crowd. |
Re: Imagine a plane is sitting on a treadmill...
At this point fire trucks might be a useful consideration.
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Re: Imagine a plane is sitting on a treadmill...
Not a single one of you has put your finger on the one obvious thing staring at you for the whole 5 or whatever pages!
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by iaink
(Post 5554860)
There is no airspeed relative to the wing, due to the motion of the rolling road/treadmill countering the forward motion of the plane from the engines thrust, so there will categorically be no lift and the hypothetical beast will remain rooted to the surface.
What the engines are doing is not relevent, if there is no air going over the wing, then there is nothing to create lift. If you turn the plane around and use the treadmill to generate airspeed without turning on the engines, it will creat lift...but it wont fly for long as once it leaves the ground/treadmill there is no forward propulsion mechanism, and drag will slow it down to the point that there is no longer enough lift to keep it in the air. This one should have died after the second post. You know they let anyone post any old crap here dont they. |
Re: Imagine a plane is sitting on a treadmill...
Originally Posted by iaink
(Post 5555774)
What idiot wrote that!
You know they let anyone post any old crap here dont they. |
Re: Imagine a plane is sitting on a treadmill...
The first and second comments were not necessarily related you know:sneaky:
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Re: Imagine a plane is sitting on a treadmill...
Originally Posted by tom17
(Post 5554071)
Imagine a plane is sitting on a massive hypothetical conveyor belt, as wide and as long as a runway. The conveyor belt is designed to match the speed of the plane exactly but moves in the opposite direction. The engines are running at take-off thrust, the brakes are off, etc. Everything is normal save for the fact the plane is on a treadmill.
Can the plane take off? Discuss :) Tom... |
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