I know it's not a typical thing for a veggie place (but then neither are any other debate topics). However based on say, all the other places I've seen this mentioned it quickly (about the 3rd-4th post after the original topic) gets to name calling and practically death threats -- so I put it here.



Just after seeing the different debates, and the way some people think... it just made me wonder about this (which the mythbusters [discovery channel show] had the results of this tonight... and the debate's even more heated)... but I digress. And I'm mainly asking this to get some non-faith related question to see if people's opinions can actually be changed (yet seems to be as vigorously debated as the bible -- no offense meant to anyone).





If you had a plane on a conveyor belt, and the conveyor belt was moving at the same speed or greater than the speed of the plane (or just able to match the plane's relative ground speed), would the plane be able to take off? [assuming the plane's going one way, the belt another -- in a similar fashion as a normal treadmill use]

^^ That is the smiley of the day. Someone used it in a post and I've been using it ever since.

Yes.

Death threats? O.o



Is the conveyor belt going against the plane or with it?

When was the conveyor belt last washed?



Are there an equal number of overweight and thin people on the plane?



Are there many exotic pets on it?

Is the plane's relative ground speed... 0?

Oh, oops... the conveyor belt would be moving the opposite direction as the plane (so plane heading east, belt moving west). Otherwise the plane would be empty (like a propeller one-two manned thing) no cargo.





[on some boards people make offers to "dispose" of some of the people if they don't think the same way they do -- it gets heated at times!]

Normally that's one of the people's answers

Basically when someone figures out how the plane will move in relation to the ground, they have the answer.



Some people say the plane will have speed in relation to the ground (i.e. it will move forward, have lift and takeoff), or that it won't have any speed in relation to the ground (i.e. it will "appear" stationary, and not have lift, therefore not take off).

heh, it humors me that people would get into a heated debate about this.



But yes, of course the plane would still lift off.

Oh. I don't think it could take off then. But a helicopter could! Or superman.

I'm not sure... I think planes might need to be moving more in relation to the air around them than the floor they're sitting on. Whether or not it's propulsion system alone is enough to lift it off I have no idea.

It normally happens when people start to explain why they believe one way or another.... I'd post the normal ways of thinking out the problem, but I'm trying not to sway people's responses yet.

I've never been that great at physics.... I suppose that air flow is being generated under the wings? Isn't that what's needed?

Whether or not a plane will lift off or not has little to do with the ground or belt beneath it. It has everything to do with the air rushing around it. Normally, when a stationary plane needs to gain this "airspeed" it involves traveling on the ground a bit.



Imagine, in the vacuum of space, that you have a plane either on a treadmill, or using rocket burners, or whatever sort of locomotion it has. If there are no air molecules pushing around the plane, it will not take off.



So, in response to the conveyor belt question:

You said the belt is going AGAINST the plane, but traveling at the same speed that the pane is moving itself. I take this to mean that the plane is actually stationary (like a person on a treadmill, or exercise bike...not really going anywhere). No, it will not take off, unless somehow, the belt itself is causing enough air movement towards the plane, which I find unlikely (<--a guess, without doing any experimentation).

they just did that experiment on mybusters on the discovery channell and the plane took off

I didn't see it.

Did they explain why?

Was the belt able to move that much air past the plane?



(P.S. I'm actually sitting 20feet away from a passenger jet. I could probably walk around and get more opinions)

Well since someone gave the answer away (although now comes the part to how people react)....



The reason why is actually simple -- the plane isn't moved forward by the wheels, the wheels are "in neutral" so to speak (i.e. they don't do anything but spin, they don't do anything for the plane other than decrease friction for the most part*). The plane is moved when air is pushed back (thrust). The conveyor belt influences the wheels, but not the engine's thrust. Basically the thing that makes the plane move doesn't have anything countering it.



Think of you on a treadmill. Set it to 10mph. Get on -- you'll have to run 10mph to keep up. Get off, then back on while standing on a skateboard (while holding the sides)-- you don't have to move an inch to keep up (yet you could move forwards and backwards with your fingers with little effort). Or picture yourself on a long conveyor belt at the airport, when you're on a skateboard and a rocket strapped to your back that propels you forward at the same rate the conveyor moves towards you (so you're heading the wrong way on the belt as it's intended to be used) you won't just stop when you hit the belt, you'll keep on going.





And this is where people normally become passionate about the "no it won't fly" or "yes it will"











* in the future, they say the wheels will be used for taxi purposes; they'll be attached to electric motors and move the plane so it can save fuel. But for now, they do "nothing".

Oh dear...one more thing that can break on these d*mn things...



I doubt it would happen anytime soon...

For one, most of the planes flying were made in the 60s, and no one really wants to buy any new ones. Esp since new ones have new problems that result in more planes falling out of the sky.



Second, the act of taxi-ing must be carried out by ground personel anyways, since the pilots can't see anything near the aircraft. Adding motors, that the pilots control, would result in ground personel having to direct the small movements at the gate anyways, but having to communicate direction verbally. (4 ft to your left...no...too far...*crunch*)

Sure for large jets, but not for smaller aircraft.

This is one of those trick questions. Trying to confuse people with the whole conveyor belt.

You're referring to personal aircrafts...I'm guessing.



But, those smaller personal prop-jobs don't have any trouble buzzing around the ramps just using their propellers...and I really don't see a need for motors in the wheels. Again, just another thing that can malfunction...and possibly lock up your landing gear.

I remember seeing a plane fly backwards across the airfield at Farnborough, by going into the wind. (I think it was a Scottish Aviation Twin Pioneer)

I think the confusing part is that the problem description makes you think that the plane's speed relative to the ground will be 0. But that's not true, because it's not the plane's wheels that push the plane forward (if it was, then the plane would definitely not take off, because it would be at rest relative to the ground). It's the air through the propellor (or the jet engine) that pushes the plane forward, even when it's taxiing and taking off. So, when the plane draws air through its engine/propellor, that air is going through at the same speed whether or not the plane is on a conveyor belt. So the plane will move forward just as if it was on the ground. And it would take off just the same.



It is similar being on skates and pulling yourself along the ground by pulling a rope. If you're pulling the rope at 4 km/h, then you're moving forward at 4 km/h. Then if you hit a conveyor belt while pulling yourself forward, you're not going to stop moving forward if you keep pulling the rope. Your skates' wheels will spin backward much faster than they were before you hit the conveyor belt, but you'll still be going forward at 4 km/h. It would of course be a different story if it was your wheels that were propelling your forward.

Death threats...over a conveyer belt.

Just to be clear though, it doesn't matter what the speed is relative to the ground, what matters is the speed relative to the air. Even if the speed relative to the ground was zero, it's possible for a plane to take off (assuming the wind speed toward the plane is large enough).

In my scientific opinion, such a scenario will violate against the normal laws of nature and thus create a vortex in spacetime, through which the Langoliers will arrive and eat us all.

Thanks SS,

I was just getting over my fear of Langoliers. Now I'll have to go right back for another 67 months of intensive psychotherapy.

Don't the wings require airflow across them to create lift? Propulsion is just to provide a way to keep airflow moving across the wing. If the propulsion is countered by another force, say a treadmill, will not the wings remain stationary?

There is no counter to the airplane's propulsion The plane's wheels can move at any (safe before exploding) speed they want but it doesn't have to be related to the plane's speed.



If a treadmill could block air-propulsion, it'd be pretty hard to explain people using fans while on them [Since either you'd be blown away using a treadmill from the wind generated by it to counter wind, or the treadmill would kill all wind making fans useless.]





Oh, and for anyone interested.... on the discovery channel's mythbuster's forum, there's the topic for this (currently 82 pages long 1636 replies): http://community.discovery.com/eve/f...6/m/4441931059