JT! Posted December 31, 2007 Report Share Posted December 31, 2007 The convayor belt moves in the opposite direction, not the mass of the plane.... at no point does the question say the plane can or cant moveThis conveyor has a control system that tracks the aircraft's speed and tunes the speed of the conveyor to be exactly the sameIt says aircrat. And the belt matches it's speed. Link to comment Share on other sites More sharing options...
ZeroMatt Posted December 31, 2007 Report Share Posted December 31, 2007 I see what you mean but the problem here is the amount of friction you are saying the wheels will cause. The largest contributing factor towards the friction acting against the plane is the air resistance, friction through tyres is much lower than you think. Link to comment Share on other sites More sharing options...
Simpson Posted December 31, 2007 Report Share Posted December 31, 2007 You see what i'm getting at?I see what your getting at yes, but planes cruise at what 500mph? and need 100 or so to take off.... frictions not masssssiveThis conveyor has a control system that tracks the aircraft's speed and tunes the speed of the conveyor to be exactly the sameIt says aircrat. And the belt matches it's speed.THE WHEELS DO NOTHING.... oh well im off out this chat now..... good points youv'e raised to discuss however Link to comment Share on other sites More sharing options...
*Tom* Posted December 31, 2007 Report Share Posted December 31, 2007 A plane needs air flowing under the wings at a certain speed to get the lift for it to take off, so if the plane isn't moving forwards, it won't take off. Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 A plane needs air flowing under the wings at a certain speed to get the lift for it to take off, so if the plane isn't moving forwards, it won't take off.That's true, the hard part is explaing how the plane can't or can move forward.The wheels do nothing UNTILL the belt starts moving at say 4000mph. Then the wheels start not to work as they did at 200mph. Link to comment Share on other sites More sharing options...
ZeroMatt Posted December 31, 2007 Report Share Posted December 31, 2007 A plane needs air flowing under the wings at a certain speed to get the lift for it to take off, so if the plane isn't moving forwards, it won't take off.That's all well and good but the plane will infact be moving forwards, on top of this the conveyor belt will be interacting with the air producing small amounts of air movement which will reduce speed required to take off. If we had some values it would be so easy to prove this Link to comment Share on other sites More sharing options...
Simpson Posted December 31, 2007 Report Share Posted December 31, 2007 so if the plane isn't moving forwards, it won't take off.Really shit the bed! Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 (edited) That's all well and good but the plane will infact be moving forwards, on top of this the conveyor belt will be interacting with the air producing small amounts of air movement which will reduce speed required to take off.You see that's something i haddn't even thought of.If the belt was moving quick enough to brake a wheel, would it create 200mph winds to lift the plane regardless? Edited December 31, 2007 by JT! Link to comment Share on other sites More sharing options...
Simpson Posted December 31, 2007 Report Share Posted December 31, 2007 The wheels do nothing UNTILL the belt starts moving at say 4000mph. Then the wheels start not to work as they did at 200mph.If the belts moving at 400, so is the plane... and so would have taken off ages before hand Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 Really shit the bed! Link to comment Share on other sites More sharing options...
ZeroMatt Posted December 31, 2007 Report Share Posted December 31, 2007 (edited) You see that's something i haddn't even thought of.If the belt was moving quick enough to brake a wheel, would create 200mph winds to lift the plane regardless?Quite possibly, depending upon the size of the conveyor. Imagine a belt thousands of miles long I'd imagine that would be able to produce some insane winds. Edited December 31, 2007 by ZeroMatt Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 (edited) If the belts moving at 400, so is the plane... and so would have taken off ages before handIf the belt is moving at 400, and the plane is at 400 also that means it's still?...but then again, the plane is at 0mph becuase i would be moving at 400mph, but it's not. Quite possibly, depending upon the size of the conveyor. Imagine a belt thousands of miles long I'd imagine that would be able to produce some insane winds.I'd guess it'd only be a bit bigger than the width of the wheels though. Edited December 31, 2007 by JT! Link to comment Share on other sites More sharing options...
ZeroMatt Posted December 31, 2007 Report Share Posted December 31, 2007 It means the plane is moving 400 mph with friction added to the equation as it would have to reach that speed with friction acting against it. So would have taken off a long time ago unless it was made of lead or something. Link to comment Share on other sites More sharing options...
*Tom* Posted December 31, 2007 Report Share Posted December 31, 2007 I don't think the plane would take off. The question has a load of flaws though, theres no figures to prove it either way, you could argue about it all day and not get anywhere. Link to comment Share on other sites More sharing options...
ManxTrialSpaz Posted December 31, 2007 Report Share Posted December 31, 2007 It's all dependant on whether you think the friction of the wheels is big or small. If you think its small, then the plane will tkae off, if you think it's big, the plane won't take off.Can we leave it at that? Unless someone has a way of proving the size of the friction. Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 It's all dependant on whether you think the friction of the wheels is big or small. If you think its small, then the plane will tkae off, if you think it's big, the plane won't take off.Can we leave it at that? Unless someone has a way of proving the size of the friction.The effect of friction increases with speed though, so the belt will just speed up and up till it was held back anyway. Link to comment Share on other sites More sharing options...
ZeroMatt Posted December 31, 2007 Report Share Posted December 31, 2007 (edited) It's all dependant on whether you think the friction of the wheels is big or small. If you think its small, then the plane will tkae off, if you think it's big, the plane won't take off.Can we leave it at that? Unless someone has a way of proving the size of the friction. I have some equations but without values they are useless. You can conclude if you were using an average plane it would take off but if the plane is different to normal in the size of the wheels, the shape of the wheels etc etc It might not take off. As this is not specified you can't say for certain. Edited December 31, 2007 by ZeroMatt Link to comment Share on other sites More sharing options...
ManxTrialSpaz Posted December 31, 2007 Report Share Posted December 31, 2007 The effect of friction increases with speed though, so the belt will just speed up and up till it was held back anyway.But, by the time the belt reaches a speed that the friction is that large, the plane would have reached takeoff speed anyway. Link to comment Share on other sites More sharing options...
JT! Posted December 31, 2007 Report Share Posted December 31, 2007 But, by the time the belt reaches a speed that the friction is that large, the plane would have reached takeoff speed anyway.No, because it wouldn't be moving. Link to comment Share on other sites More sharing options...
tomturd Posted December 31, 2007 Report Share Posted December 31, 2007 Assuming no friction...The speed of the treadmill is irrelevant. It could be going backwards at a 100,000mph, and the thrust of the engines generating 200 mph of forwardness (its been a while since I did physics), would just mean the wheels would be travelling at the equivelent of 100,200mph. It makes no difference.. the plane would still go forwards (and take off) Link to comment Share on other sites More sharing options...
adamtrials Posted December 31, 2007 Report Share Posted December 31, 2007 Assuming no friction...The speed of the treadmill is irrelevant. It could be going backwards at a 100,000mph, and the thrust of the engines generating 200 mph of forwardness (its been a while since I did physics), would just mean the wheels would be travelling at the equivelent of 100,200mph. It makes no difference.. the plane would still go forwards (and take off) And even with friction, the wheels are only going to be turning twice as fast as normal. (Plane's takeoff speed = X, speed of conveyer is -X, Speed of wheels = 2X), and I reckon most plane wheels are capable of turning at least twice the takeoff speed.Also as the speed increases, the plane generates more lift, meaning the wheels have less weight resting on them, thus less friction. Link to comment Share on other sites More sharing options...
feest Posted December 31, 2007 Report Share Posted December 31, 2007 (edited) SCOPSE HAS IT ENTIRELY CORRECTOfcourse it doesn't take off!What a stupid analogy! You silly lesbians.To put it simply..... if the treadmill/conveyer belt is matching the speed at which the wheels are turning, then the plane doesnt actually move anywhere. (think of a rolling road/dyno) So if the plane isn't physically moving forwards then there is no air passing over the wings. If there is no air passing over the wings then the plane can't take off.It'd be a different scenario if the plane needed 100 KPH to take off and the plane was not moving but there were gusts of wind at 100 KPH blowing towards the plane, there's a reason why planes fly into the wind when they take off. It reduces their take off speed, 30 KPH headwind means they only need to get to 70 KPH.I could just be going off on a tangent here and I haven't answered the question, because I didn't read the question. Edited December 31, 2007 by feest Link to comment Share on other sites More sharing options...
Haz Posted December 31, 2007 Report Share Posted December 31, 2007 SCOPSE HAS IT ENTIRELY CORRECTExcept that it does take off, of course... Link to comment Share on other sites More sharing options...
Tomm Posted December 31, 2007 Report Share Posted December 31, 2007 In the old thread I was offering an alternative scenario and I think I confused a few people, possibly including JT But the plane can't move forward because the original question says that it can't.Read the original scenario again:An aircraft is standing on a runway that can move (a conveyor belt). The aircraft moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the aircraft's speed and tunes the speed of the conveyor to be exactly the same, but in the opposite direction. There is no wind. The pilot begins to add thrust to the engines...The conveyor belt tracks the speed of the plane and the speed of the belt is the same as the speed of the plane. It says nothing about cancelling its speed or keeping it still. So it can move. I think you've confused quite a few people.SCOPSE HAS IT ENTIRELY CORRECTLoads of people do. Scopse isn't really one of them because he's answering the wrong question It's a completely obvious question unless you misread/misunderstand the scenario.I wish people would stop chatting about friction. Like I said before, it's completely hypothetical so talking about friction is stupid. Why not talk about how it's impossible to get a big enough treadmill or a situation with no wind or a system that tracks the plane's speed in real time, instantly. You have to ignore things like this Link to comment Share on other sites More sharing options...
Willy Posted December 31, 2007 Report Share Posted December 31, 2007 It will take off... Link to comment Share on other sites More sharing options...
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