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Post by rocket88 on Jul 21, 2009 12:53:31 GMT
Answer me this; If I stood on the ground next to the plane/treadmill, would the plane be moving forwards in relation to my stationary position ? If you answer YES, please explain how it's capable of moving forward (in relation to a stationary object), when it's on a treadmill which cancels out any forward movement. [/b][/quote] YES YES YES! The whole point is that the TREADMILL CANNOT cancel out any forward movement! In essence the plane will take off the same if its on a treadmill or on a normal runway as the wheels are independent of its engines and therefore will just spin faster as the treadmill moves faster. Why people can't get their head around this is beyond me?!!?[/quote] Changed me mind again!!! YOU WIN!!! ;D ;D ;D I LOSE!
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Post by thepremierbanksy on Jul 21, 2009 13:01:51 GMT
YES YES YES! The whole point is that the TREADMILL CANNOT cancel out any forward movement! In essence the plane will take off the same if its on a treadmill or on a normal runway as the wheels are independent of its engines and therefore will just spin faster as the treadmill moves faster. Why people can't get their head around this is beyond me?!!? Changed me mind again!!! YOU WIN!!! ;D ;D ;D I LOSE! In which case you either assume that the wheels are frictionless, or you calculate the friction in the whees - the extra work done to double the wheel speed will be made up from the kinetic energy of the plane, provided by the thrust from the engines. If the difference is enough then the plane won't get to the required threshold to take off, and it will end up smashing into whatever is at the end of the runway.
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Post by neoisd1 on Jul 21, 2009 13:11:01 GMT
If the plane does 100mph & the belt does 100mph in the opposite direction, the wheels will be rotating as if they were doing 200mph, but the planes going nowhere. No no no! The plane will be going forward! The thrust of a plane has no relation to the ground, it moves through the AIR. Think of its wheels as just big fucking stabilizers to keep the plane steady at slow speed, and as with stabilizers on a child's bike they are free spinning and help in no way to move it forward.
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Post by rocket88 on Jul 21, 2009 13:16:23 GMT
I have the definitive answer. The plane will ............................
Maybe take off. I should have been a polutician.
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Post by lurcherman on Jul 21, 2009 15:30:52 GMT
Yes, it will just need more power than usual. e.g ...... on a calm day = more power or longer time to get airbourne Into a head wind = less power or shorter time.
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myatt
Academy Starlet
Posts: 194
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Post by myatt on Jul 21, 2009 17:31:46 GMT
Having only just seen this, I think you are all missing the point! Its obviously an impossible situation, to which there is no answer. The plane has to take off becuase the engines act on the air and there is no force to stop it moving forward. It cannot take off due to the fact that it won't move forward due to the treadmill. Both reasons are 100% vaild. It does make you think though! The engines are on and displace air, but that air does not pass under the wings are create uplift. The plane will not take off, nor is it an impossible situation. Of course its an impossible situation - how can you build a treadmill that travels infinitely fast!? Anyway, the point was that you are perfectly correct, but so are the people who say yes! Imagine a plane on a treadmill moving at a set speed - how would it influence the plane taking off? It would make no difference as the plane is powered by a jet engine which alters the speed of the plane relative to the air - not the ground. Hence, when the pilot switches on the engines it moves the plane forward regardless of what the wheels are doing. Like i said both answers are correct which is the point of the question!
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Post by rocket88 on Jul 21, 2009 17:57:24 GMT
I reckon it would take off.
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Post by edinburghstokie on Jul 21, 2009 22:55:35 GMT
Just re-read the question & I've changed my mind. No, it can't take off, because of this bit >"but as it moves forward, the conveyor belt senses the speed of the plane's forward motion and instantaneously moves at exactly the same speed in the opposite direction". If the conveyor belt instantaneously cancels out the forward motion, then the plane is in fact at a standstill in relation to the ground. It's got nothing to do with the speed of the wheels, the question states that it's the PLANES forward motion that is detected & compensated for by the belt. The plane is effectively rendered stationary & won't take off. If it is doing 100mph in one direction, it certainly isn't stationary! The question doesn't say that the speed is cancelled out by the treadmill.
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Post by rocket88 on Jul 22, 2009 1:21:59 GMT
Just re-read the question & I've changed my mind. No, it can't take off, because of this bit >"but as it moves forward, the conveyor belt senses the speed of the plane's forward motion and instantaneously moves at exactly the same speed in the opposite direction". If the conveyor belt instantaneously cancels out the forward motion, then the plane is in fact at a standstill in relation to the ground. It's got nothing to do with the speed of the wheels, the question states that it's the PLANES forward motion that is detected & compensated for by the belt. The plane is effectively rendered stationary & won't take off. If it is doing 100mph in one direction, it certainly isn't stationary! The question doesn't say that the speed is cancelled out by the treadmill. Owrate mate, the plane would go like fook propelled by it's jet engines, the treadmill would be goin like fook, but YES the plane would move forwards & take off because it would have forwards motion irrespective off the motion of the treadmill. The treadmill would have to be as long as a normal runway tho, so that the aircraft could build up enough speed to gain lift. IE, YES, THE PLANE WOULD TAKE OFF!!!! ;D ;D ;D ;D ;D QED ? ??? ;D ;D ;D
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Post by fazza90 on Jul 22, 2009 11:33:30 GMT
Yes
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Post by thepremierbanksy on Jul 22, 2009 11:49:04 GMT
The engines are on and displace air, but that air does not pass under the wings are create uplift. The plane will not take off, nor is it an impossible situation. Of course its an impossible situation - how can you build a treadmill that travels infinitely fast!? Anyway, the point was that you are perfectly correct, but so are the people who say yes! Imagine a plane on a treadmill moving at a set speed - how would it influence the plane taking off? It would make no difference as the plane is powered by a jet engine which alters the speed of the plane relative to the air - not the ground. Hence, when the pilot switches on the engines it moves the plane forward regardless of what the wheels are doing. Like i said both answers are correct which is the point of the question! Well to be fair a plane doesn't travel infinitely fast, so neither would the treadmill have to, it is theoretically possible to build this treadmill that goes up to 100mph+. Anyway I'm off to hang my head in shame at not answering the question properly in the first place
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myatt
Academy Starlet
Posts: 194
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Post by myatt on Jul 22, 2009 17:16:50 GMT
Of course its an impossible situation - how can you build a treadmill that travels infinitely fast!? Anyway, the point was that you are perfectly correct, but so are the people who say yes! Imagine a plane on a treadmill moving at a set speed - how would it influence the plane taking off? It would make no difference as the plane is powered by a jet engine which alters the speed of the plane relative to the air - not the ground. Hence, when the pilot switches on the engines it moves the plane forward regardless of what the wheels are doing. Like i said both answers are correct which is the point of the question! Well to be fair a plane doesn't travel infinitely fast, so neither would the treadmill have to, it is theoretically possible to build this treadmill that goes up to 100mph+. Anyway I'm off to hang my head in shame at not answering the question properly in the first place If you don't realise that the treadmill has to be infinitely fast then you havn't understood fully the problem - try reading the whole thread!
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Post by neoisd1 on Jul 22, 2009 17:40:52 GMT
Can't believe this is still going :-)
The plane will take off. The end.
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Post by rocket88 on Jul 22, 2009 18:08:35 GMT
Can't believe this is still going :-) The plane will take off. The end. Are ya sure ? ;D
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Post by neoisd1 on Jul 22, 2009 18:16:31 GMT
Can't believe this is still going :-) The plane will take off. The end. Are ya sure ? ;D ha ha ;D ;D ;D Please stop
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Post by rocket88 on Jul 22, 2009 18:21:17 GMT
I've really enjoyed this thread mate. ;D I started off saying an emphatic NO the plane won't take off, & by the end I'd turned full circle. This is what's good about public forums/debate. I was wrong, & I learned something. ;D
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Post by edinburghstokie on Jul 22, 2009 20:27:31 GMT
I'm trying to think of a future suitable question.
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Post by Northy on Jul 22, 2009 20:38:16 GMT
I've really enjoyed this thread mate. ;D I started off saying an emphatic NO the plane won't take off, & by the end I'd turned full circle. This is what's good about public forums/debate. I was wrong, & I learned something. ;D so my first post on the bottom of page 3 "yes it will" was accurate then, I'm not bad at these multiple choices ;D
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krazy
Youth Player
Posts: 359
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Post by krazy on Jul 22, 2009 21:08:59 GMT
Nooooo - its not possible!!!! Rocket, how can you change your mind???
I get the point about the wheels but the fact is a plane does not "levitate" in mid air waiting to get some forward propulsion (movement in case its spelt wrong)...I cannot get my head around how the plane can get moving if the treadmill cancels out the wheels moving. Surely no air will be passing over the wing fast enough
Aaaargh - I'm determined to sleep tonight
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Post by kidsgrove4 on Jul 23, 2009 1:59:16 GMT
I am an aircraft engineeer by trade, and apart from your ridiculously stupid question . The answer is NO. If I have to start talking ailerons and air movement across a static object , we'll be here for hours, but no it can't. . Nuff said. Anyone who says otherwise is a fucking moron. No offence.
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Post by rocket88 on Jul 23, 2009 2:20:34 GMT
Ya doing my fuckin bonce in now!!! Fuck off, the lot of ya!!!!
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Post by RWChris on Jul 23, 2009 4:45:13 GMT
I'm currently training to be an airline pilot so i'd say i'm kinda qualified to have a say on this The answer is NO.
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Post by edinburghstokie on Jul 23, 2009 6:34:23 GMT
I'm currently training to be an airline pilot so i'd say i'm kinda qualified to have a say on this The answer is NO. Please tell me which airline you will be working for, and I'll make sure I don't bother flying with them.
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Post by edinburghstokie on Jul 23, 2009 6:36:19 GMT
I am an aircraft engineeer by trade, and apart from your ridiculously stupid question . The answer is NO. If I have to start talking ailerons and air movement across a static object , we'll be here for hours, but no it can't. . Nuff said. Anyone who says otherwise is a fucking moron. No offence. Please state where it is in the original question that it states that the forward motion of the aircraft is cancelled out by the backward moving treadmill.
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Post by kidsgrove4 on Jul 23, 2009 6:49:19 GMT
I am an aircraft engineeer by trade, and apart from your ridiculously stupid question . The answer is NO. If I have to start talking ailerons and air movement across a static object , we'll be here for hours, but no it can't. . Nuff said. Anyone who says otherwise is a fucking moron. No offence. Please state where it is in the original question that it states that the forward motion of the aircraft is cancelled out by the backward moving treadmill. That's the point Einstein. If you are on a fucking treadmill you aren't going fucking FORWARD. For fucks sake stop being a freaking nongoid. Good thread tho. NOT !!!!!!!!!Unless its a harrier fighter it won't fucking work.
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Post by lawrieleslie on Jul 23, 2009 6:50:13 GMT
If you are running on a tread mill at 8mph and the tread mill is set at that speed you will have no forward movement. If you increase your own speed to 10mph you will have forward movement of 2mph. Lets look at a plane with take off speed off 140mph. It will have to be travelling 140mph faster than the speed of the conveyor belt travelling in opposite direction to allow the plane to take off. If the conveyor belt travels with the plane then the plane will take off once the combined speed of it and the conveyor belt reaches 140mph. So given the right conditions the plane will take off. Air has to be passing over the wings and control surfaces at 140mph to get lift off.
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Post by edinburghstokie on Jul 23, 2009 7:47:16 GMT
That's the point Einstein. If you are on a fucking treadmill you aren't going fucking FORWARD. For fucks sake stop being a freaking nongoid. Good thread tho. NOT !!!!!!!!!Unless its a harrier fighter it won't fucking work. Using insults isn't going to help your argument. Imagine this. You are on roller skates on a treadmill. A friend (off the treadmill) puts a hand on your back to stop you going backwards. You turn on the treadmill. You stay stationary, your wheels underneath you move freely, your friend has to exert no extra force, (maybe a minute bit extra to overcome friction in the skates bearings). The treadmill is going at 10 mph backwards. You are stationary. Your friend now adds a tiny extra bit of constant force to your back. You move forward. The treadmill is going at 10 mph backwards you are going forward at 1 mph. All relative to a fixed point of reference. Not the treadmill. An aircraft is the same. The wheels roll freely, the extra force is the engines and it accelerates forwards. The question is designed to fool people into thinking that the speeds are cancelled out, but an aircraft isn't powered forward by it's wheels, (how would it fly forward in the air then).
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Post by thepremierbanksy on Jul 23, 2009 10:43:52 GMT
Well to be fair a plane doesn't travel infinitely fast, so neither would the treadmill have to, it is theoretically possible to build this treadmill that goes up to 100mph+. Anyway I'm off to hang my head in shame at not answering the question properly in the first place If you don't realise that the treadmill has to be infinitely fast then you havn't understood fully the problem - try reading the whole thread! OK I don't have time to read 8 pages, but i've read the question again and had a think, and I still don't see where infinite speed comes in. The question states that the treadmill will sense the speed of the plane (fuselage not wheels) and move at the same speed (in the opposite direction of course), so the plane will accelerate up to (for example) +150mph, and the treadmill will accelerate to -150mph. The wheels will be rotating at the equivalent of +300mph. Where does infinite speed come into it? If the treadmill senses the speed of the wheels then I guess you could get into a situation of positive feedback, but that's about a good as an explantion I've got. please explain!
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Post by RWChris on Jul 23, 2009 10:50:50 GMT
But the aircraft will take off due to the lift generated by the wings.
The conveyor belt, in this problem, is running at a speed to cancel the aircrafts thrust (a zero groundspeed). The aircraft is not going to be moving in relation to the airflow so will not generate the lift to lift off.
Now if you had a REALLY strong headwind then in theory an aircraft can lift off at zero groundspeed when it reaches a speed called VLOF (the lift off speed...this is an aerodynamic speed).
Unless I'm misunderstanding the question I can't see how the answer can be 'Yes'.
I'm sitting an Air Transport Pilot License exam in Principles of Flight in October so hope to god i'm right!!
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Post by thepremierbanksy on Jul 23, 2009 10:58:42 GMT
But the aircraft will take off due to the lift generated by the wings. The conveyor belt, in this problem, is running at a speed to cancel the aircrafts thrust (a zero groundspeed). The aircraft is not going to be moving in relation to the airflow so will not generate the lift to lift off. Now if you had a REALLY strong headwind then in theory an aircraft can lift off at zero groundspeed when it reaches a speed called VLOF (the lift off speed...this is an aerodynamic speed). Unless I'm misunderstanding the question I can't see how the answer can be 'Yes'. I'm sitting an Air Transport Pilot License exam in Principles of Flight in October so hope to god i'm right!! I thought the same, but the crux of the question is that the force pushing the plane forward is created by the thrust from the jet engines (or propeller I guess), whilst the wheels are assumed to be free-wheels and certainly the forward force is not created by the wheels. Therefore when the treadmill is going in the opposite direction to the thrust of the plane, the wheels will just rotate faster than they would on the runway. kind of assume that the wheels are frictionless, or that the force required to turn them faster is negligble.
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