mind boggling

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mind boggling
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flag nateb
FL
Posted: Dec 23, 2007 at 23:24 Quote
"The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation"

Taken from the first post, the original question.

Ok - plane fires jet engine, wheels rotating speed has to increase, this we agree on, the statement above says the conveyor will simply match it's speed, by whatever means, that we don't need to know. Black magic, voodoo, witchcraft, whatever, it JUST does, so what? Now you still have a plane moving forwards just with wheels and a treadmill turning a little faster than before, like youtube guy said, the rotating speed of the treadmill (and therefor the wheels) has absolutely no impact on the situation.....

"The conveyor belt is designed to exactly match the speed of the wheels at any given time" to me does not say this speed is not allowed to increase, all it does say is that when the rotating speed of the wheels does increase (at that very instant, or simultaneously, same thing) the conveyor will also increase it's speed to match. ..... because of that, once again, yes the plane can move forwards and therefor fly.

Also, once again, this comes down to more of an english language argument than a physics one. The question is not inclusive enough to limit the scenario to make you right, it doesn't state "the speed of the wheels or the conveyor can not change, can the plane take off?" It simply says the conveyor will always match the speed of the wheels. Once again, if it were a car, you would be right, stationary object. Car with a jet engine on the roof, forward movement.

nate
flag draco
Posted: Dec 24, 2007 at 1:35 Quote
oh. my. god.

I have the correct answer. I had it on page 3 or whatever. I have had the question posed to me in class.

Here is the deal - and its the real answer, its not me being a jackass:

the question itself creates rules in which traditional physics laws would have to be broken in order to achieve anything.

The question is only a medium for discussion - THERE IS NO CORRECT ANSWER EXCEPT FOR THAT THE QUESTION PREVENTS THE ANSWER.

for example: as the question states, the conveyor will perfectly match the wheels speed at any time - so, regardless of thrust being unrelated to wheel rotation, the plane doesnt move. The very real workings of thrust are cancelled out by a rule written in the problem - any time thrust is invovled to propel the plane forwards, the wheels would HAVE to be moving faster than the conveyor belt.

Do you guys understand that? Its not that the thrust isnt there, and its not that if the plane were on ICE it wouldnt take off... it would.. but the problem states that no matter what, the wheels are matched in speed. This means that even with the thrust on full tilt, which would physically move the plane in any toher circumstance, whoever wrote the question has posed a situation that would not occur normally - the wheels.

You guys understand that if the wheels are turning at the same speed as the belt, that the plane cannot move forwards righT? any forwards movement of the plane (caused by thrust, nuclear explosions, hand of god) would translate into the wheels spinning faster than the treamill!!

Think really long and hard, and outside the box. Normal physics do not apply because the question has a 'law' built into it that prevents the rest of the story from happening.

it is not about the physics of any of it - its a word problem designed to see who is reading it properly - and none of you are.

I am not wrong about this. REread it, and think about what I said.
flag dirt-jumper-tom
Posted: Dec 24, 2007 at 4:04 Quote
draco wrote:
oh. my. god.

I have the correct answer. I had it on page 3 or whatever. I have had the question posed to me in class.

Here is the deal - and its the real answer, its not me being a jackass:

the question itself creates rules in which traditional physics laws would have to be broken in order to achieve anything.

The question is only a medium for discussion - THERE IS NO CORRECT ANSWER EXCEPT FOR THAT THE QUESTION PREVENTS THE ANSWER.

for example: as the question states, the conveyor will perfectly match the wheels speed at any time - so, regardless of thrust being unrelated to wheel rotation, the plane doesnt move. The very real workings of thrust are cancelled out by a rule written in the problem - any time thrust is invovled to propel the plane forwards, the wheels would HAVE to be moving faster than the conveyor belt.

Do you guys understand that? Its not that the thrust isnt there, and its not that if the plane were on ICE it wouldnt take off... it would.. but the problem states that no matter what, the wheels are matched in speed. This means that even with the thrust on full tilt, which would physically move the plane in any toher circumstance, whoever wrote the question has posed a situation that would not occur normally - the wheels.

You guys understand that if the wheels are turning at the same speed as the belt, that the plane cannot move forwards righT? any forwards movement of the plane (caused by thrust, nuclear explosions, hand of god) would translate into the wheels spinning faster than the treamill!!

Think really long and hard, and outside the box. Normal physics do not apply because the question has a 'law' built into it that prevents the rest of the story from happening.

it is not about the physics of any of it - its a word problem designed to see who is reading it properly - and none of you are.

I am not wrong about this. REread it, and think about what I said.

And i've been trying to exactly back what you said up.

Just this Nate guy beleives that because a physist says it can happen it can.

Wrong.


bigquotesSo why wouldn't the conveyor just speed up as the wheels rotation also does? If the conveyor is designed to do so, then the only reason it wouldn't, or couldn't, if it's design or construction was flawed.....and yet the car / plane would still be moving forwards because there is an outstanding force (from either your finger on the toy car or the jet engine on the plane) in the forward direction......


The conveyor would speed up, exactly as the question states it will speed up to match the wheels rotation at anytime.
This 'outsanding force' or your example of thrust on the aircraft is flawed, because this force isn't on the conveyor or attatched to the aircraft.

So in retrospect, if this was a real experiment, you would be simulating the hand of god coming down from the heavens above and pushing the plane and puting it at the other end of the runway.

Anotherwords, your "thrust" is static to the movement of the conveyor, which if it was connected the aircraft, it wouldn't be.

Then this brings me back to the point that if the plane was to move forward, at somepoint the energy transfered to the wheels would be a faster rotation that what the 'matching opposite rotation' would be, and thus you would be breaking a rule.



bigquotes1) If a plane had frictionless wheel bearings could it sit at a stand still on a conveyor spinning in the opposite direction?

To bad they dont exist.
And even if the bearings were 'frictionless,' there would still be friction from the tires to the conveyor.

bigquotes2) If you answered yes to the above question - could it sit at a stand still on the same conveyor spinning in the opposite direction at 1,000,000 km/h?

No because the wheels would simply blow up and the aircraft would be propelled backwards at no less than 1,000,000 km/h and would seize to exist.

bigquotes3) If you also answered yes to that question, why would the plane not move forwards when the jet engine was fired up?

Because the conveyer would still continue to speed up.

bigquotes4) The only way the plane wouldn't move forwards when the jet engine was fired up, regardless of the turning of the conveyor belt (at any speed, the same as the wheels, less than the wheels, more than the wheels, it doesn't matter, forget about the f'in spinning wheels) is if there were an equal but opposite force also acting on the plane to counter act the jet engine, like say an insane head wind. No opposite force, yes the plane moves forward.

No because the opposing force is the conveyor speeding up preventing the aircraft from making any ground.
You tried to use the water-plane as an exaple of the wheels beeing irellevent, but what you dont take into concideration is the sea, or hell the roation of the planet, does not change speed to match the force trying to push the plane forwards.

bigquotes5) I already know your reaction to that above statement, "oh but the wheels will spin and the plane won't move." Seriously, if we were talking about a vehicle powered by the wheels like a car, you would be right, but we're not, so someone has to justify this statement or just stop making it, it's getting old.

I already have done several times, go back and read my posts.

[Quoten]Perfect, you are in college, ask your instructor. Report back their thoughts. In the mean time, maybe read a few of those links I posted before you so quickly shoot back your generic bs post about the spinning wheels. Really, they must be shiny for you to be so hung up on them. Like a kid with a.d.d.

nate[/Quoten]

And with this post you lost all respect and now you look like a fool.

Anything you contributed to the thread after this I completly overlooked as I hope everyone else should.

Good effort.


See how all this goes around in circles Nate? it's exactly what the question was designed to do.

In respect, the person who wrote the question is alot more intelligent than the hundereds of phsysists who tried to find a solution are.

The solution is simple Nate, there isn't one.
flag brad-maxwell
Posted: Dec 24, 2007 at 4:45 Quote
that is what i have been saying for the bast 3 threads to nate, i even reffer back to dracos original post on page 6.

thanks for backing me up, im positve on this one.........i think Blank Stare
flag nateb
FL
Posted: Dec 24, 2007 at 8:45 Quote
dirt-jumper-tom wrote:
because this force isn't on the conveyor or attatched to the aircraft.


So the jet engine isn't attached to the aircraft? Dude, this conversation would be like if you went to see the Calgary Stampeders play the BC Lions, and rather than just watching you decided you should get in on the game. Like the football game, you should have remained a spectator in this discussion. You don't have the intellect to add anything useful.

Draco, I do see the point you are making....something I thought about, but maybe not enough or in the right way..... It is possible, but I am still not sure I agree with it 100%, but I totally see why you guys have a leg to stand on in the debate...

As for Mythbusters, if they have chosen a plane and conveyor tow vehicle that are capable of accelerating at the same rate up to the planes required take off speed, to me that suggests a true test of the debate inspiring question.....

I'm out. Right or wrong the only thing I feel stupid about is letting an internet argument get to me so much. The rest of you can hopefully understand my message to you in this song.



nate
flag dirt-jumper-tom
Posted: Dec 24, 2007 at 11:02 Quote
[Quote="-nate-"]
dirt-jumper-tom wrote:
because this force isn't on the conveyor or attatched to the aircraft.


So the jet engine isn't attached to the aircraft? Dude, this conversation would be like if you went to see the Calgary Stampeders play the BC Lions, and rather than just watching you decided you should get in on the game. Like the football game, you should have remained a spectator in this discussion. You don't have the intellect to add anything useful.


You completly misunderstood what I said.
I was relating to your finger on the toy car you used as an example.

As for your claims I don't have any interlect to add anything useful, i'm yet to see you prove any of my theories wrong, or comeback with any decent argument against, this includes your moronic football game scenario you just tried to suggest.

To sum up, well i'm not even going to bother, your not worth the waste of my time anymore.

However I did have a nice little giggle to myself at the idiotic message you sent me in spite of being completly wrapped up in your own conclusionless, useless, and unfounded theorys.

I know i'm right, and many people proberly agree.

I'm not going to let the small percent of people who fail to understand when they are wrong get to me.

I'll just leave you with this.

Unsecure image, only https images allowed: http://www.ehponline.org/docs/2005/113-2/crybaby.jpg

Merry Christmas.
flag draco
Posted: Dec 24, 2007 at 17:19 Quote
nate you've been here forever. don't you remember the last thread like this? 38 pages of everyone arguing it to the death, before the conclusion was reached.

If you eliminated variables within the problem, then you could have answers.

For example, if the plane was on a conveyor spinning backwards at the speed the plane needs to take off, will the plane take off?

Yes, because thrust is unrelated to wheel speed.


or, if a plane had no engines, and was accelerated to the speed it needs to take off, powered by the wheels, would it leave the ground?

Yes, but only until drag brought it back below that speed.


but as soon as the plane changes its relation to the starting point, it's breaking the laws of the question.

I will try to mathematize it up for a sec.

If the plane needs to hit 100kmh to lift off, then its forward speed needs to be 100kmh. In another situation, in a 100kmh windstorm, the plane would lift the ground, even with the engines off.. thats how paper planes and gliders work.

but, if the conveyor matches the wheel speed exactly, with no delay, here we go:


lets assume this fact, which is a fact: If you are pushing a cart on a treadmill at 5mph, and the belt is doing 5mph, then, you are stationary in relation to an object NOT on the treadmill. Your forward speed is zero.

If you speed up the treadmill to 10mph and are running with the cart, even tho you are running at 10mph, you are still stationary compared to the ground.

The Only Way to change your speed, is to accelerate with no regard to the treadmill - if you begin to run faster than the treadmill, you will move in relation to the ground! Thus, if you are on the treadmill at 10mph, you are moving zero in relation to the ground. but if you run at 12 mph on the treadmmill while it is moving at 10mph, you have a 2mph forward movement in relation to the ground.

That however, is a 2mph acceleration over the treadmill - thus, it would not be perfectly matching your speed.

So you see, its a trick question. It writes in a 'rule' of which can not be broken.

This even further can be broken down.

[Quoten]You are in a windowless room. There is one door out of the room. there are no vents or other ways out. The door is latched, but unlocked. Your hands are tied, there is a knife on the table next to the door. You may not touch the door in any way. The walls are thick steel. You have a tomato, a magnifying glass, a bottle of water, and a hammer.

Can you get out of the room?[/Quoten]


think about it, and then tell me the answer. and when you have that answer, you'll ahve the answer to this one.

anyone?
flag srobinson
Posted: Dec 24, 2007 at 23:06 Quote
^^worst example ever. while you are right about the fact that it is not physically possible for the conveyor and the wheels to move the same speed at all times, that example has absolutely nothing to do with a plane. it still assumes the fact that the plane is powered by the wheels.

The only way this situation is possible is if there is a computer that reads the speed of the wheels and puts that speed on the conveyor belt.

The problem lies in the fact that even if it were possible, there is no such thing as instant reaction. There will always be a fraction of a second where the computer reads the data, processes and outputs to speed up the treadmill. Thus there is a fraction of a second were the wheels are spinning faster than the treadmill.

Let's put it this way. If the plane is moving forwards at 10kph relative to the ground, the wheels, assuming it is on normal ground, are spinning at 10kph.

now this is where we hit the snag. the plane is doing 10k, so the wheels spin at 10k, the computer then runs the conveyor backwards at 10k. now one is doing 10k forward, the other 10k backwards, so the wheels are now doing 20k. the comp reads this, 20k on the conveyor, wheels now spinning 40k. and on we go to an infinite number until something blows.


hope that made sense, too damn tired
flag crkt
Posted: Dec 24, 2007 at 23:12 Quote
leave computers out of this equation buddy, this is a hypothetical question unless you know of any mile long conveyor belts capable of speed fast enough to "prohibit" an aircraft from taking off.

so just think hypothetically not how it is literally impossible for the experiment itself to actually work
flag srobinson
Posted: Dec 24, 2007 at 23:15 Quote
hypothetically, everything works. don't go there.
flag odin333
Posted: Dec 26, 2007 at 9:07 Quote
z-man wrote:
blakey wrote:
No it can't, because there is no air moving over the wings to create lift.
but why wouldn't it move? the propulsion comes from the jets, not the wheels

because the jet engines are the thing that creates the propulsion. the wheels just make it easier for the plane to take off as they reduce friction and drag. but he main purpose of the jet engines are to force the plane forward creating air movement over the wings, which, at the correct speed, would cause the plane to enough drag of the wings, which would force the plane upwards. but without the forward movement, their is no air flow over the wings, which in terms means no drag, no lift.

if its for an essay or school question, feel free to use those exact words.

 


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