Tony Harrison Posted February 22, 2006 Report Share Posted February 22, 2006 And snappel... since when have you had anything to with aircraft? A wing and prop DO use the same principle to create lift, forming low pressure on the bottom and high on the top. Believe me - I did my A2 physics coursework on lift. And if a prop didnt create lift like a wing then why would you adjust the pitch of the prop to create different amounts of forward lift?Well, as it happens I did a BEng in engineering, including a fair few modules from the Aerospace course. And, in fact, I did well in all of them. By different principle I was referring to how they work as part of the aircraft - one staying still in relation to the aircraft, and the others turned. Perhaps you misunderstood me. My problem was that if a plane is stationary in reference to the ground, revving the (nose mounted) propellor will not, on its own, create enough draft to lift the plane. If the plane rolls forward thanks to that draft, then we're getting into bog standard aerodynamics.But that's all irrelevant right here. The plane flies. If you can't see that, then I'm assuming you failed the A2 Physics coursework. Link to comment Share on other sites More sharing options...
PaRtZ Posted February 22, 2006 Report Share Posted February 22, 2006 so basically with the plane, the only thing that is happening is that it has no velocity, cos its on the conveyor belt. And cos its a jet engine it doesn't need the aerofoil effect to occur on its wings to take off; it just needs air surrounding the engine to "suck in and spit out the back to propel it"Have I got brains? Link to comment Share on other sites More sharing options...
Tony Harrison Posted February 22, 2006 Report Share Posted February 22, 2006 Of course it needs the aerofoil effect! The plane has velocity - all the conveyor belt does is turn the plane's wheels. For Christ's sake, it's so simple!The conveyor belt does not stop the plane moving forward under it's thrust, no matter how fast it (the belt) is moving. Link to comment Share on other sites More sharing options...
PaRtZ Posted February 22, 2006 Report Share Posted February 22, 2006 bah never liked physics anyway Link to comment Share on other sites More sharing options...
andyroo Posted February 22, 2006 Report Share Posted February 22, 2006 Well, as it happens I did a BEng in engineering, including a fair few modules from the Aerospace course. And, in fact, I did well in all of them. By different principle I was referring to how they work as part of the aircraft - one staying still in relation to the aircraft, and the others turned. Perhaps you misunderstood me. My problem was that if a plane is stationary in reference to the ground, revving the (nose mounted) propellor will not, on its own, create enough draft to lift the plane. If the plane rolls forward thanks to that draft, then we're getting into bog standard aerodynamics.But that's all irrelevant right here. The plane flies. If you can't see that, then I'm assuming you failed the A2 Physics coursework.Yeah I wasnt saying the plane would pull itself along how that guy said iit would, you just described a helicopter and i pointed it out...But anyway... as the thrust of the plane increases, and the conyeyor belt just speeds up as well? I'm presuming the conveyor belt has no top speed or anything? It will get to a point where the friction in the wheels will cause heat in the bearings and melt them?We are also assuming the thrust of the engines is more powerful than whatever is driving the conveyor belt? Link to comment Share on other sites More sharing options...
Krisboats Posted February 22, 2006 Report Share Posted February 22, 2006 I'm not "being stubborn and not opening my mind" but i don't get what your arguments are on about. If theres no friction on the wheels, then the plane is effectively floating isn't it? doesn't that make the conveyer belt irrelevant?But if the conveyer is running at the right speed to counteract the plane from going forwards, With all the planes weight being on the wheels it would mean that if they were being counteracted from spinning, then the plane wouldn't be able to go anywhere... The plane needs to roll first to take off so it can get its required air lift over the wings. But if its being stopped from rolling it won't have any lift so will not take off. I don't get what oli means by saying that the plane will just be able to have thrust and lift off... it needs to roll first but it's being stopped from rolling so if theres no forwards motion then the plane won't have any wind going over the wings so it can't just take off.If you could try explaining a bit more clearly then i would most likely get it, try using bullt points or something, it would help me out loads. Link to comment Share on other sites More sharing options...
nmt_oli Posted February 22, 2006 Report Share Posted February 22, 2006 (edited) you still dont seem to understand the relation ship between the plane and the conveyor properly. the thrust has NOTHING to do with the wheels and the conveyor will only move as fast as the plane is moving, and since a plane will take off at less then 200mph the conveyor wont go over 200mph, the max speed the wheels will turn is 400mph.Sorry, that was directed at andyroo- not krisboats Edited February 22, 2006 by nmt_oli Link to comment Share on other sites More sharing options...
nb88 Posted February 22, 2006 Report Share Posted February 22, 2006 So is the conveyer belt counteracting the speed of the wheels or the speed of the plane? if it counteracts the speed of the wheels surely it wont go anywhere? Unless it starts sliding forwards because of the thrust? Link to comment Share on other sites More sharing options...
nmt_oli Posted February 22, 2006 Report Share Posted February 22, 2006 Kris- the plane is not being stopped from going anywhere! read the Q and my previous answers carefully. Link to comment Share on other sites More sharing options...
Tony Harrison Posted February 22, 2006 Report Share Posted February 22, 2006 Ok, I'll try another approach. The conveyor doesn't stop the plane rolling. Yes, the wheels turn twice as fast, but the thrust from a jet engine is so huge in comparison to the friction of the wheels it can still move in relation to the ground and fly off.As for wheels/bearings melting, this is a theoretical problem, but I would guess that the plane would fly off before that occured. Of course, we can't tell as we aren't specifying materials, operating conditions or anything else.The question was simple - fly or not.The answer is fly. Link to comment Share on other sites More sharing options...
nmt_oli Posted February 22, 2006 Report Share Posted February 22, 2006 So is the conveyer belt counteracting the speed of the wheels or the speed of the plane? if it counteracts the speed of the wheels surely it wont go anywhere? Unless it starts sliding forwards because of the thrust?Speed of the plane, if it was the speed of the wheels you get a paradoxical situation- read snappels link. Link to comment Share on other sites More sharing options...
Krisboats Posted February 22, 2006 Report Share Posted February 22, 2006 I did read it and unfortunately it was too long and complicated for me to continue reading without getting like so your saying because its measuring the speed of the plane and the plane is going nowhere, the conveyer belt will also be going nowhere so the plane will be able to take off because the conveyer belt is still? Link to comment Share on other sites More sharing options...
Will Arnold Posted February 22, 2006 Report Share Posted February 22, 2006 yes, it will fly, as there is nothing but the friction in the bearing and maybe slight brake rub slowing it down yes IT WILL FLY! Link to comment Share on other sites More sharing options...
tipsy Jock Posted February 22, 2006 Author Report Share Posted February 22, 2006 Whoa, i go out for one ride and get 4 pages of respones! Most of you are trying to overcomplicate this by far! Snappel, Nmt_oli and a few others have got it though. Firstly the means of propulsion doesn't matter, also a propeller will not create enough thrust to create the aerodynamic effect over the wings nessecary to take off. Even with the belt moving in the opposite direction the plane will take off because the plane will just move along the belt as if it were a normal runway albeit with the wheels turning twice as fast as normal. Thats not a very good explanation, took me a while to figure it out as well Link to comment Share on other sites More sharing options...
nb88 Posted February 22, 2006 Report Share Posted February 22, 2006 explain more please...draw a diagram, lol Link to comment Share on other sites More sharing options...
Will Arnold Posted February 22, 2006 Report Share Posted February 22, 2006 explain more please...draw a diagram, lolu dont need a diagram, just read over what pete just said Link to comment Share on other sites More sharing options...
Krisboats Posted February 22, 2006 Report Share Posted February 22, 2006 Whoa, i go out for one ride and get 4 pages of respones! Most of you are trying to overcomplicate this by far! Snappel, Nmt_oli and a few others have got it though. Firstly the means of propulsion doesn't matter, also a propeller will not create enough thrust to create the aerodynamic effect over the wings nessecary to take off. Even with the belt moving in the opposite direction the plane will take off because the plane will just move along the belt as if it were a normal runway albeit with the wheels turning twice as fast as normal. Thats not a very good explanation, took me a while to figure it out as well That still doesn't make sense the conveuyer is designed to counter act the plane going forwards, so this would mean the wheels would be spinning twice as fast, but then if you accelerated the conveyer does as well so the wheels are still going twice as fast as the conveyer but its not going anywhere. I really don't get what you mean. Link to comment Share on other sites More sharing options...
Tony Harrison Posted February 22, 2006 Report Share Posted February 22, 2006 You don't need to know this. If your brain can't work it out, you're best of letting go. Or you might explode. Honest. Link to comment Share on other sites More sharing options...
Will Arnold Posted February 22, 2006 Report Share Posted February 22, 2006 That still doesn't make sense the conveuyer is designed to counter act the plane going forwards, so this would mean the wheels would be spinning twice as fast, but then if you accelerated the conveyer does as well so the wheels are still going twice as fast as the conveyer but its not going anywhere. I really don't get what you mean.its the jet engines that makie the plane go forwards, so the wheels can spin as much as they goddam want with no effect, meaning it will take off nomatter how fast the wheels spin Link to comment Share on other sites More sharing options...
tipsy Jock Posted February 22, 2006 Author Report Share Posted February 22, 2006 That still doesn't make sense the conveuyer is designed to counter act the plane going forwards, so this would mean the wheels would be spinning twice as fast, but then if you accelerated the conveyer does as well so the wheels are still going twice as fast as the conveyer but its not going anywhere. I really don't get what you mean.The wheels have no effect on whether a plane can take off or not they're only there to stop the prop hitting the ground, for example very early planes had skids instead. So although the belt speeds up the only effect of this is that the wheels will turn twice as fast as they would normally during take off. Link to comment Share on other sites More sharing options...
Krisboats Posted February 22, 2006 Report Share Posted February 22, 2006 I beleive the human brain can work out anything if its explained to me properly and clearly. That was a bit patronising snappel, i'm not a kid Link to comment Share on other sites More sharing options...
oakley Posted February 22, 2006 Report Share Posted February 22, 2006 Friction has a lot to do with it. think about this problem simply, and read my posts again- ive already said this.THE PLANE DOES MOVE. if the plane is stationary, so is the conveyor- but for the conveyor to move, the plane MUST move, as the speed of the conveyor is controlled by the speed of the plane NOT the speed of the engines.The wheels of a plane hold it off the ground and spin freely, therefore a conveyor will not move a plane. In reality, a plane on aconveyor belt will move due to friction in the wheels- however, as soon as the force from the trust equals the frictional force inthe wheels, the plane will become stationary with the conveyor moving underneath it- but that doesnt relate to this problem as in this problem if the plane was stationary, the belt would stop.right, the plane WOULD take off as it is just thrust that moves the plane. the plane wheels would move twice as fast as the conveyor belt, but then the conveyor belt would catch up and then the wheels would go twice as fast as that again, so the wheels and conveyor belts would be moving at incredible speeds by the time the plane had taken off BUT it wouldnt stop the plane taking off as it is thrust that makes planes fly.Think of the plane flying, but with its wheels out, the wheels dont help it fly, they could be held still but it wouldnt stop the plane flying.i know what i mean any way! joE! Link to comment Share on other sites More sharing options...
Krisboats Posted February 22, 2006 Report Share Posted February 22, 2006 Oh i think i get where you guys are coming from now. But i don't think its right though.right, the plane WOULD take off as it is just thrust that moves the plane. the plane wheels would move twice as fast as the conveyor belt, but then the conveyor belt would catch up and then the wheels would go twice as fast as that again, so the wheels and conveyor belts would be moving at incredible speeds by the time the plane had taken off BUT it wouldnt stop the plane taking off as it is thrust that makes planes fly.Think of the plane flying, but with its wheels out, the wheels dont help it fly, they could be held still but it wouldnt stop the plane flying.i know what i mean any way! joE!oh rite, so you're saying theres a delay with the conveyer belt matching the speed of the plane? where'd you get that idea from, wouldn't it be instant if the speed is being matched? Link to comment Share on other sites More sharing options...
Simon Posted February 22, 2006 Report Share Posted February 22, 2006 But, surely, if i understand this, the conveyor is going as fast as the plane should be going if it was moving, therefor keeping it still?It's just running on a running machine, there is no wind resistance or anything, and thats how a plane takes off, with the wind going by the wings and creating a vacuum.So it can't possibly take of, unless the riddle is twisted and saying the plane does actually move along the belt (like if you run on those belts at the airport when going to your terminal).So it won't take off, unless the riddle is a trick riddle and doesn't explain itself. Link to comment Share on other sites More sharing options...
nb88 Posted February 22, 2006 Report Share Posted February 22, 2006 ah i can sorta get it now, i think...the conveyer belt would only have an effect on the speed of the wheels...and theyre seperate, so theyll just spin faster than normal and the plane will move forwards Link to comment Share on other sites More sharing options...
Recommended Posts