Can Plane Take Off

Discussion in 'The Classics 97.3' started by TheWand_foh, Jul 22, 2016.

  1. TheWand_foh shitlord

    TheWand_foh
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    Not so much a picture post, but you guys should have some fun.

    This has been all over the web, and has caused a lot of controversy.. and even a few lay offs..

    Heres the scenario...

    An airplane is on a conveyor. The conveyor is set to match the speed of the airplane in the backwords direction. However fast the plane moves, the conveyor moves just as fast.

    Can the plane take off?

    (yes, I know the answer to this, but a shocking amount of people do not)
     
  2. Tuco Well-Known Member DONOR

    Tuco
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    So if one were to stand beside the conveyor belt, they could stand next to the plane, and the plane would not be moving, yet the wheels of the plane would be moving at a speed to have the plane take off?

    I think the answer is obvious, if you know the ideas of lift.

    It"s yes, if the plane is a harrier, or some other plane with V-Thrust, no otherwise, imo.
     
  3. Matt the Gimp_foh shitlord

    Matt the Gimp_foh
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    Where we"re going we won"t need roads.
     
  4. TheWand_foh shitlord

    TheWand_foh
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    the plane is not a harrier, or V-take off .. just a normal plane, can range from small to large, or even have a propellor or jet engine.
    not giving answer till more polls are in.
     
  5. Zeste_foh shitlord

    Zeste_foh
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    no.

    the wings are not moving through the air, so there"s no lift.
     
  6. Lambourne_foh shitlord

    Lambourne_foh
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    The only thing that matters is the speed of the aircraft relative to the air.
     
  7. Brodda Thep_foh shitlord

    Brodda Thep_foh
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    Amazingly you could argue both ways.

    Technically, you cannot use a conveyor to hold a plane stationary that is trying to take off (Not unless you made it so incredibly fast that the friction created by the wheels turning is enough to negate the thrust of the engines. Which would probably be so fast that the rubber would tear apart. or the bearings would melt.)

    So yes and no. If the plane truly stood still there would be no vertical thrust generated which would mean the plane could not take off. But then, there is no way you could use a conveyor to hold a plane still, thus it would accelerate nearly normally and take off. (the wheels would just be spinning significantly faster than a normal take off.)
     
  8. Hippos II_foh shitlord

    Hippos II_foh
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    Yo that swat kats plane could take off EZ, I voted yes.
     
  9. TheWand_foh shitlord

    TheWand_foh
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    Oh man.. Broda is so close

    Can see the wheels turning (no pun intended)
     
  10. Matt the Gimp_foh shitlord

    Matt the Gimp_foh
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    tha universe wuld kollapz lol
     
  11. Lambourne_foh shitlord

    Lambourne_foh
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    Comes down to what definition of "matching the speed" you use really. Does it match the airspeed or the speed relative a stationary outside observer.
     
  12. Brodda Thep_foh shitlord

    Brodda Thep_foh
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    Here is a post that anyone can understand. This question was either created by someone that thought he was being tricky but screwed up or is a trick question to try and get people to focus on something that is irrelevent to the problem.

     
  13. qxx_foh shitlord

    qxx_foh
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    Come on, the idea of the converyer belt is to state its properties and we aren"t supposed to be taking its chemical and physical composition in mind. It"s the abilities of a converyer belt we"re after. Jesus. And, this is the most retarded "tricky but obvious" question I"ve ever read.
     
  14. LISeru_foh shitlord

    LISeru_foh
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    Without knowing this, you can"t answer the question. This isn"t obvious.
     
  15. Brodda Thep_foh shitlord

    Brodda Thep_foh
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    You have to ask yourself what the point of the question was.

    Was it to demonstrate to people not knowing how lifts and forces work that jets and props do not generate any vertical lift by themselves and thus a plane not moving relative to the air will not fly no matter how fast the props spin or how hard the jets blow? (though I am sure some small amount of vertical lift is generated by moving all that air around, but still not enough to fly?

    Or was it a trick question to see how many people actually think a conveyor belt could hold a plane still relative to the ground interacting only with freely rotating wheels?
     
  16. TheWand_foh shitlord

    TheWand_foh
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    well sadly, I dont know the origin of the question since its so wide spread.

    However, most people tend to belive (as the poll is starting to reflect) that a conveyor can be built that is able to hold a plane in place.

    Being on wheels, a plane is technically "always" on a conveyor. The wheel speed has nothing to do with the forward momentum. (as they have no gears and spin freely)

    So the plane will simply accellerate forward despite the wheel speed untill its moving fast enough to take off.

    The whole conveyor thing is nothing more than an illusion.
     
  17. Metranon_foh shitlord

    Metranon_foh
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    the plane will take off

    say the plane moves at 250 miles per hour at takeoff. it"s using jet engines which generate thrust against the non-moving air around it

    on a normal (non-conveyor belt) runway, the wheels will spin at the speed of the plane (250 mph) and the plane will accelerate forward up to 250 mph until it achieves sufficient foward speed to take off

    if the runway beneath it moves backward at 250 mph, the plane"s wheels will simply spin at 500 miles per hour, because the plane is creating 250 mph forward thrust against the air. The conveyor belt is not producing thrust against against the plane or the air, but only against the wheels, which (assuming little or no friction) spin on their bearings twice as fast because of the two competing forces. The plane however, doesn"t rely on friction created by the wheels with the ground to create thrust, but instead creates forward thrust because of the friction caused by forcing air at extremely high pressure through it"s engines (in the case of a propeller) or in the case of a jet it creates thrust by Newton"s third law of action and reaction. A gas, or working fluid, is accelerated by the engine, and the reaction to this acceleration produces a force on the engine pushing or accelerating it forward through the air.

    so if you could stand right outside the plane (ignoring jet thrust, the conveyer belt, etc), the plane would appear to move forward at 250 MPH and take off. as it took off, the wheels would spin at 500 mph.

    this of course all ignores the friction on the highly vulnerable surfaces of the wheel and the bearings inside it, which is obviously impoosible, i.e. trick question
     
  18. GaliemVaelant_foh shitlord

    GaliemVaelant_foh
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    The wheels don"t have to be powered, and no thrust needs to be directed toward them.


    Aye, there is no need to consider the plane"s chemical composition. The answer to this question lies in these three universal laws.

    The result would be the same with either a jet or prop plane. The engine or propeller pushes against theair, not the conveyor belt. As a result, the air pushes back against the airplane (Newton"s Third Law).

    Due to the shape and design of the plane, this creates vertical thrust, despite the plane"s standing completely still.

    There is a caveat here in that the plane"s lifting off would require a higher terminal air velocity than if it were moving. Anyone who has ever flown understands why. When a jet is taking off, the first thing that the pilot does is burn the engines to create an initial vertical lift. Some runway is needed to lift off because the breaks on the landing gear are not strong enough to absorb the force required for take off.

    In this case, the only caveat to taking off with both horizontal and vertical acceleration without eating up any runway or coveyor is the conveyor"s ability to negate the plane"s movement relative to the ground. The reason for the higher required terminal air velocity is that energy and momentum being transfered from the air to the plane is, in turn, being transfered from the plane to the conveyor in some small fractions, and that energy is being used.

    To contrast, energy transfered to the ground would be much more dampened by the Earth"s mass if the conveyor belt were not there, and thus without the belt, the system would not bleed energy the way that this one does.

    The important fact here, though, is that the plane is still being pushed on by the air.

    The actual math for this is fairly non-linear, as the mass of the plane is changing along with everything else.

    A scaled down model of this experiment would make an awesome toy IMHO.
     
  19. TheWand_foh shitlord

    TheWand_foh
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    Galiem, There are a few little videos of this.. i"ll try to find a link if I can hunt it down.

    I been talking to a few of the guys from mythbusters and trying to get them to do this myth on air.

    Its a rather heated topic over there. In fact, it was so big they removed it all together from the fan club site. Only available to the members and science guys atm. .. fortunately, im one of them
     
  20. GaliemVaelant_foh shitlord

    GaliemVaelant_foh
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    It"s a fairly interesting experiment, to be honest. I"ve made conjectures based on Newton"s Laws, but the escence of physics lies in systems behaving differently than our intuition would lead us to expect.

    Since I don"t know enough about planes to sketch the math for this, or even a realistic enough free body diagram, I"m left only with the laws themselves.

    I would absolutely love to see those guys tackle this one, even if their budget only allowed a scaled down version of the experiment. The principles would be the same with a model plane, I"d assume, so long as all the plane"s thrust originates from jets or props.