You could link to one. There are lots of good file hosting site.pinkmouse said:
Try
http://www.yousendit.com/
It's the easiest.
leave #1 empty - just do #2 and #3 and copy the url.
'til tomorrow - need sleep.
OK it's late and I may have gone on a bad tangent . I'm sleepy but I think I concede that by decoupling the wheels, the plane could move down the run way and take off even with its wheels turning the wrong way.
BUT, there still is a problem: for the plane to move down the runway, its wheels have to move faster than the belt which is not allowed in this scenario. The plane still stays on the ground since it can't get down the runway.
BUT, there still is a problem: for the plane to move down the runway, its wheels have to move faster than the belt which is not allowed in this scenario. The plane still stays on the ground since it can't get down the runway.
Lostcause said:
ok, lets see what we can agree on.
Given scenario:
There is an airplane of some sort with an attached axle sporting a sweet set of wheels, which are free to rotate, yet have no tendancy of their own to do so.
The plane has an engine which moves air backwards, tending to pull itself forwards.
This plane, like most, also has some sort of wings fixed to it. These provide lift to the plane, provided there is enough air moving past them.
Let's assume that no reasonable plane can move enough air over its own wings to provide lift at a stand still.
There is a runway-length conveyer belt attached by its axles to the earth in some manner, such that its surface is free to move, but the whole belt does not translate along the earth. Think conveyer belt, not tank track.
The plane is situated on its wheels on this conveyer belt in such a manner that the axis of rotation of the plane's wheels and that of the belt are parallel.
The tires on the plane are made of some sort of material which provides sufficient friction under the weight of the plane, that they will not slip on the belt.
The belt is designed in such a manner as to exactly match the "speed" of the wheels. For example: if the wheels have a perimetric speed of 1 m/s, the belt moves at 1 m/s in the opposite direction.
There is no noticable wind on the "runway"
Is that all good?
Ok, so plane starts up its engine.
There is a pulling action on the plane.
The plane begins to roll forward.
But wait, the belt must roll backward at the same rate.
The air traffic contoller, seeing a plane sitting on the runway revving its engine, radios to the pilot "what's up? You're not going anywhere, get a move on!"
The pilot gives the plane more gas.
The engine says "I think I can, I think I can" and starts spinning faster.
But it can't. Every time the plane tries to move forward, the belt moves backwards the same amount.
The plane can not move forward (in relation to all of its surroundings, save the belt).
The pilot says "WTF?"
The tires eventually blow.
The pilot stops the engine, gets out and wonders why the (now motionless) runway is so bloody hot.
Max
By meaning I couldn't post a video, I should have actually said I can't take one. My digital camera and cellphone are both decidedly old or low tech.
In my experiment, the wheel and the paper are directly coupled through friction, (unless I pulled really hard on the paper, of course), so the radial velocity of the wheel exactly matches the horizontal velocity of the paper, thus fulfilling your criteria.
Night-night RDFan, and don't have nightmares about planes and runways! 🙂
In my experiment, the wheel and the paper are directly coupled through friction, (unless I pulled really hard on the paper, of course), so the radial velocity of the wheel exactly matches the horizontal velocity of the paper, thus fulfilling your criteria.
Night-night RDFan, and don't have nightmares about planes and runways! 🙂
pinkmouse said:
Ah, but you broke the rule by not moving the paper fast enough and running out of paper to pull on.
"Imagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation."
Max
Max you're assuming things. How do you know what paper I used, and how fast I moved it?
I have proved to my satisfaction that the general case, i.e. the acceleration of the axis of the wheel laterally, is decoupled from any rotation of the wheel or motion of the runway. The hypothesis stated in the experiment is merely one case of this general rule.
Max, it's easy, try it for yourself!
:edited for clarity:
I have proved to my satisfaction that the general case, i.e. the acceleration of the axis of the wheel laterally, is decoupled from any rotation of the wheel or motion of the runway. The hypothesis stated in the experiment is merely one case of this general rule.
Max, it's easy, try it for yourself!
:edited for clarity:
maxro said:
The opposite direction of rotation..........thats the key to your own argument.
However it is still irrelevant!
Just to clear up your own argument draw it on a piece of paper and put the direction of rotation on it....the opposite direction actually turns with the wheel not against it...believe me just draw it.
Oh sod it, to be perfectly honest I'm not sure what your argument is anymore.
Initially my only reservation was that the wheels would blow out...that was very wrong and in the distant past. The fact is that the belt matches the speed of the wheels and even if this was zero...(the paradox)...it stil makes no difference to the fact that the plane is moving. It just means that the wheels are doing something strange whilst it gains airspeed. (remember, they are not coupled together other than to stop the plane falling onto the ground before it gains enough airspeed to lift off)
The thing is guy's, the wheels are a red herring, it's a trick question designed to invoke a tangential reasoning that does not exist in the first place.
Sleep well!
Initially my only reservation was that the wheels would blow out...that was very wrong and in the distant past. The fact is that the belt matches the speed of the wheels and even if this was zero...(the paradox)...it stil makes no difference to the fact that the plane is moving. It just means that the wheels are doing something strange whilst it gains airspeed. (remember, they are not coupled together other than to stop the plane falling onto the ground before it gains enough airspeed to lift off)
The thing is guy's, the wheels are a red herring, it's a trick question designed to invoke a tangential reasoning that does not exist in the first place.
Sleep well!
AudioFreak said:
To quote parts of my earlier posts.... Ok we conclude that C is not possible if we are to fulfil *all* the criteria of the original question. So we are left with A or B. A the plane goes nowhere, B it takes off. I can't see any other possible ways of fulfilling *all* criteria of the original question.
Audiofreak, if the enterprise had wheels would it be able to take off? Or would a plasmic space tear swallow it up?
Lostcause said:
I already drew it and posted it back in post 88
Note that back then I was wrongly thinking that the belt could conteract the force of the engines, and after thinking about something not unlike pinkmouses experiment (though kinda in reverse) I realised my error, however I thought that in some of my later posts at least maybe explained how one could reasonably come to either of the two conclusions, based on whether the question is about jet propultion or relative motion, and how one chooses to interpret the speed of the wheel, apparently not 😉
edit: if you look at my arrows you will see one is turning clockwise and the other anticlockwise, that to me is in opposite directions 🙂
Tony.
And ok I must concede that even B might be considered to be breaking the rules set down in the orignal post in that although at least to some degree plausible, the belt speed would not be equal to the wheel speed. So the only option left if you want to absolutely adhere to the original (flawed) question, then the plane goes nowhere.
AudioFreak said:
Ahh but option B falls into the same category as C as if the belt is moving and the wheels aren't (except if we talk about linear speed of the wheel ie it's forward moving speed which actually can only match the speed of the belt if it is not turning and the belt is moving forward)...
hehehe I think we have a winner just put on the breaks and pull the belt forward 😉
hmmmm dan posted as I was typing 😉
Tony.
Seems incredibly simple this one.
First picture a car, doing the same experiment. The car should remain stationary.
Because the force is applied via the wheels...and the force on the wheels wheels is exactly opposite.
Now take the plane. It's propulsion (force) is via the thrust of it's engines. There is no force
on the wheels at all.
Just a bearing..which has practically zero friction (The bearing in effect nullyfies the effect of the conveyor belt)
Thus the conveyor belt does not influence the airoplane significantly at all.
This leaves just one force having an influence on the movement of the aeroplane..and that is the thrust of it's engines. The only
significant force on the the plane that counteracts the force of the motors is the friction of the air.. Thus the airoplane will take off!!
Those who think the airoplane remains stationary are actually saying that the conveyor belt has a force on the airoplane that nulls the force of the motors which is ridiculous ofcourse.😀
First picture a car, doing the same experiment. The car should remain stationary.
Because the force is applied via the wheels...and the force on the wheels wheels is exactly opposite.
Now take the plane. It's propulsion (force) is via the thrust of it's engines. There is no force
on the wheels at all.
Just a bearing..which has practically zero friction (The bearing in effect nullyfies the effect of the conveyor belt)
Thus the conveyor belt does not influence the airoplane significantly at all.
This leaves just one force having an influence on the movement of the aeroplane..and that is the thrust of it's engines. The only
significant force on the the plane that counteracts the force of the motors is the friction of the air.. Thus the airoplane will take off!!
Those who think the airoplane remains stationary are actually saying that the conveyor belt has a force on the airoplane that nulls the force of the motors which is ridiculous ofcourse.😀
This is strange, maybe it's only a few of us that see it this way but whatever happens to the wheels the plane still moves.
The only other feasible solution is that the wheels are tuning so fast that they blow out and....crash.
If you can prove the science of this then you can stop the plane taking off.....that was my original stance and is still niggling me!!!!
The only other feasible solution is that the wheels are tuning so fast that they blow out and....crash.
If you can prove the science of this then you can stop the plane taking off.....that was my original stance and is still niggling me!!!!
There are only 3 actors in this scene. So simple math will do.
Thrust of the motor is A (100)
Friction of the bearing B (1)
Air friction C(50)
A forward
B against
C against
+100-1-50=49 forward
+A-B-C=FORWARD
The fact that it is going forward causes air to flow over the wings..creating a low pressure above the wing..sucking the airoplane into the air!
Thrust of the motor is A (100)
Friction of the bearing B (1)
Air friction C(50)
A forward
B against
C against
+100-1-50=49 forward
+A-B-C=FORWARD
The fact that it is going forward causes air to flow over the wings..creating a low pressure above the wing..sucking the airoplane into the air!
The question is brilliant. It's collectively wasted countless hours of our time, and on many other forums I see...maxro said:
Max, you were breaking it down methodically until you got to here: "The plane begins to roll forward. But wait, the belt must roll backward at the same rate. The air traffic contoller, seeing a plane sitting on the runway revving its engine, radios to the pilot 'what's up? You're not going anywhere, get a move on!' "
For the non believers, a thinking exercise to disprove:
Picture the plane without wheels/landing gear and held up by a crane. Apply thrust and it will move.
Now picture some wheels attached to the <b>side of the plane</b> sliding on a vertical conveyor wall with the same properties as in the question. Is the plane's forward motion impeded by how the wheel's spin? I don't see anything governing the forward thrust of the plane affected by what happens to the wheels.
Now put the conveyor horizontally and add put the wheels on the bottom of the plane (plane's weight is still held up by the crane). Any change?
Bas whilst technically correct the devil is in the details (or in this case the lack thereof) 😉 there is unfortunately more than one way to interpret the question 😀
since anyone joining the thread now has very likely not read all previous posts, Ill link to my post about the ways I think the question can be interpreted, I think you should read it too lostcause 😉
http://www.diyaudio.com/forums/showthread.php?postid=776846#post776846
I believe the plane will take off, I also beleive that it is possible to argue that it won't based on interpretation of the question, and ignoring actual physics of propultion (after all does the question say that the laws of physics apply here????)
Tony.
since anyone joining the thread now has very likely not read all previous posts, Ill link to my post about the ways I think the question can be interpreted, I think you should read it too lostcause 😉
http://www.diyaudio.com/forums/showthread.php?postid=776846#post776846
I believe the plane will take off, I also beleive that it is possible to argue that it won't based on interpretation of the question, and ignoring actual physics of propultion (after all does the question say that the laws of physics apply here????)
Tony.
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