Brain Teaser

Discussion in 'Off Topic' started by csmguitarman, Oct 25, 2007.

  1. MBK2

    MBK2 New Member

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    Therein lies the entire problem. You're question is made to sound as if the plane's thrust would be countered by the treadmill 'exactly'. So if the jet engine starts up and tries to move one inch forward, the treadmill counters by returning the plane one inch, thus rendering the plane motionless.

    Now you are sounding as if you're saying the plane is at full thrust from a standstill and the plane never actually 'rolls' the first few feet.
    You are in essence saying that the planes engine out-thrusts the treadmill in those first few feet, yards, etc.
  2. MBK2

    MBK2 New Member

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    So you're saying that the plane wouldn't actually roll in contact with the treadmill the first 100 yards?
  3. Noonagon

    Noonagon New Member

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    The plane would probably not take off actually, but not due to insufficient airflow but due to the fact that if the conveyor belt would match the speed of the planes wheels then the wheel would spin at an infinate speed and probably blow up befre takeoff. :)
  4. MBK2

    MBK2 New Member

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    See.... now we are adding variables upon the original question. The question was made to sound as if it was 'always' going to exactly opposite.

    Better question...

    If we put an odometer on the planes wheels, and the plane accelerated in any speed you'd like.....will the odometer read 100 yards after the thrust of the planes engine pushes the plane forward 100 yards??
  5. MBK2

    MBK2 New Member

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    I think I see now that csmguitarman meant something else, but his wording on the orignal question didn't convey that...

    Here is where the differing views are coming in...

    Say the plane is sitting there on the treadmill. Then the treadmill fires up to 100 mph 'instantly'. Csmguitarman is saying that the initial thrust of the treadmill instantly going to 100 mph will cause the free-rolling planes wheels to react by spinning in place a bit because of the initial treadmill thrust. So he is saying that though the plane would go with the treadmill overall, it will also slightly roll forward a bit in relation to the treadmill (lets just say 1 mile forward for the sake of the discussion) due to the wheels free-rolling manner...Am I correct Csmguitarman??
    So in essence after one hour the plane would have only actually have moved backwards 99 mile, because it free-rolled forward 1 mile in relationship to the treadmill. 100 mph rearward by the treadmill -minus 1 mile forward by the planes free-rolling wheels =equals 99 mph rearward.

    Now here's the difference in our views...

    Would not the treadmill sense that the plane had free-wheeled forward 1 mile and compensated to 101 mph to 'match' the planes forward progress, thus actually making the plane 100 miles rearward after that 1 hour???
    Because your original question was worded to sound that the treadmill will match the planes' forward movement.

    I think 'that' is where the question is misunderstood because it is poorly worded in relation to what csmguitarman was trying to convey.
  6. csmguitarman

    csmguitarman New Member

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    The question says match not counter. Since the wheels are free spinning they cannot transfer acceleration from either treadmill or plane. The question simply states a cause effect/ reaction relationship. When one goes a certain speed the other goes the same in the opposite direction. The question doesnt say anything about the treadmill being able to force the plane stationary. Some people just assume that and that is why they form and incorrect answer.

    Are we on the same page yet?

    And i am not saying out thrust. They simply thrust.
  7. csmguitarman

    csmguitarman New Member

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    No it would read 200. The wheels take into account the planes forward movement/speed and the treadmills rearward. Remember neither the treadmill nor the plane put and "drive on the wheels. The wheels simply react to both forces
  8. csmguitarman

    csmguitarman New Member

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    I have never met someone that made this so complicated for them selves no offense.

    What is the treadmill doing 100mph for if the plane is not.

    The planes wheels will roll forward but the plane will be moving backward and not at the same rate the treadmill is because of the wheels.

    Like i said i really am exhausted trying to get you to understand. I posted this question for ever and a day ago and it had spread fairly well across the internet. Its wording has never changed, and no one else had ever had a problem with its wording. They either did or didnt understand the principles at work, but no one has ever tried re wording the question so that they could understand the answer.
  9. MBK2

    MBK2 New Member

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    I'm glad that you didn't bail on me Guitarman, because I really want to know if I am truly wrong and see if there really was something that I missed about all this.

    I have read your responses briefly and think I have some important details that may shed some light for either you or me.

    Unfortunately I'm at the office and my mind is a bit occupied so I'd be better able to word my questions better on my regular PC later.

    I'm not trying to fight but rather find out if it truly is me that can't see something.

    I'll be the first to admit when I misundersood something..as I did in the JBED Opera Mini thread.

    Ciao for now and will post in a few hours.
  10. Noonagon

    Noonagon New Member

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    The treadmill will only move when the plane does, at no other time will this treadmill move. the problem here is that the wheels will be spinning at an infinate speed because they are free rolling, so until the friction force from the wheel bearings reaches the thrust force from the jet engines the plane will move forward. Wether or not this plane will reach lift speed is some sort of differential equation. The wheels will always be spinning faster then the treadmill. So I have a few questions:

    1. are these magic wheels that can spin infinitly fast?

    2. can this treadmill spin infinitly fast?

    3. does the plane have a limited amount of thrust?
  11. MBK2

    MBK2 New Member

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    I think that the original question was posed vaguely on purpose to spark the debate for and against.

    It is intentionally worded to get people into thinking that the treadmill will 'counter' the planes forward movement, thus keeping it place.

    That leads into the debate where analogies muddy the waters and we start comparing distance to distance, and speed to speed.

    What the question actually sets-up and eventually the answer saying that the plane would take off anyways, is that the plane would out-thrust the treadmills counter-effect.

    One scenario I had in my mind really made me see what Csmguitarman (and others agreeing with him) is implying.

    The scenario would be that the plane is sitting in place on the treadmill(that hasn't started moving yet) with the engines fired up but with the brakes applied, so the plane is going 0 mph.
    Now the treadmill starts up and builds gradually to 10, 30, 60, 100mph...but the brakes are taken off and the planes' jet engines thrusts to keep the plane in place in the middle of the treadmill. So in effect the plane is going 0 mph while the treadmill is going 100 mph. And that goes on and on, keeping the plane in the same spot in reference on the treadmill. Plane 0 mph, treadmill 100 mph....not equal speed-wise. thus, the jet engines need only to apply a little more thrust to get it moving forward. So now the planes thrust is moving the plane 10 mph while the treadmill is still at 100 mph. Still not equal, but the plane is moving forward.

    So you're point of view is that the treadmill could be going 180 mph, doesn't matter because the plane's thrust could keep the plane at 0 mph regardless of the treadmills speed, and that it could apply enough thrust to get the plane to 180 mph while the treadmill is still 180 mph, but the plane is still moving forward 180 mph and going to take off.

    I see your point of view.

    But our point of view is that, in that scenario, the only way the plane stays in place while the treadmill is going 180 mph is for the jet engines to be exerting the equivalent of 180 mph thrust. Thus 'matching' to keep the plane in place.

    Thats where it gets real muddied...
  12. Noonagon

    Noonagon New Member

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    It will match the speed of the planes wheels and not the plane if it matched the speed of the plane this whole debate means nothing. I am saying the same thing as you but the treadmill will match the wheels speed and not the planes. If it just matched the planes speed there would be no question as the plane would definitly take off due to eas free rolling of the wheels themselves. :)
  13. MBK2

    MBK2 New Member

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    This one is wrong...as I mentioned, things start to get muddy...

    If the plane rolled forward and the treadmill went in reverse 100 yards at the same time, then the odometer would only read 100 yards. Test it out for yourself with an experiment.

    Simple physics, but that's another debate that we both probably can do without,,,LMAO:wink:
  14. MBK2

    MBK2 New Member

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    I refer you back to the original questions' wording.

  15. Noonagon

    Noonagon New Member

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    well then there is no problem for the plane to takeoff. it jsut means that the planes wheels will spin at twice the speed of the conveyor and the only thing the plane needs to over come is bearing friction.
  16. csmguitarman

    csmguitarman New Member

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    This question is still tricking you................ As soon as the planes engines apply thrust.....it will start moving forward. No matter how fast the treadmill moves. Since it applies its trust to the air, there is now way for the treadmills matching speed to be applied to the plane to be able to hold it in place.

    And yes, the odometer would read 200. Since the wheels spin the planes forward movement plus the treadmill backward, it would read both distances traveled by both, and since they both went 100 yards. it would read 200. The plane would have travel 100 yards forward and the treadmill 100 backward. The plane and treadmill starting points would be 200 yards apart.
  17. Noonagon

    Noonagon New Member

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    csmguitarman FTW
  18. MBK2

    MBK2 New Member

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    The wording of the question is meant to be mis-interpretated, that is where the this whole debate went awry. I was interpretting it as the planes attempted movement forward was matched by the treadmill.

    Perhaps I'm supposed to interpret the question your way, but because of it's wording I still see it as
    ...if the treadmill moves in reverse 10,30,60 mph...the only way the plane can 'stay in place' is to apply 10, 30, 60 mph forward thrust.



    Sorry...it's 100 yrds,
    If the plane is rolling 100 yards, while the treadmill is going in reverse 100 yards, the plane spins in place only 100 yards.
    This can be easily tested by using any free-rolling item and pulling whatever it's rolling on in reverse.
  19. Noonagon

    Noonagon New Member

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    But if the plane accelerates to move 100 yards then the treadmill moves 100 yards and the wheels spin 200 yards.if you use a free wheeling piece and move it forward 1 foot RELATIVE TO THE GROUND which is the whole point of this arguement, and the treadmill moves backward 1 foot the the wheel moved 2 feet.
  20. MBK2

    MBK2 New Member

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    Guy, if only the treadmill moved 100 yards in reverse the plane's wheels aren't spinning. Do you get that part atleast??
    Let me say it another way...If the plane is sitting there on the treadmill and the treadmill goes 100 yards backwards, the planes wheel odometer would say 'ZERO'...the only way then to get the odometer to say 100 yards is with the planes' forward 100 yrd roll...Am I making sense to you??...LOL:tounge:

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