Mythbusters tonight

[Zeek]

Originally Posted by Mainerunr

correct except that if the wheels and treadmill are moving at the same velocity, opposite direction, then the plane is stationary with respect to the air and thus cannot take off.

Please stop saying the same thing over and over. The treadmill is going to increase in speed relative to the speed of the aircraft. Go out and buy a toy plane with wheels. Go to the gym and turn on a treadmill. While holding the plane, run it up the treadmill with the treadmill at 3mph. Next try it again at 5mph. Go ahead and try it at 10mph.

Now ask yourself, did your arm have to go faster to move the plane up the treadmill at the same rate while the treadmill was set at 10mph or 3mph? No? Well that's exaclty what will happen when the engines push the plane. The plane will move forward and the FREE SPINNING wheels will simply go faster. The engines don't have to work any harder.

[djpain75]

Simple guys... without lift the plane isn't going anywhere. If the plane is on a treadmill then the plane really isn't moving is it... only the treadmill is moving, the plane is stationary. Stationary plane = no lift... no lift the plane ain't goin nowhere. Pretty simple

Who cares about the wheels / treadmill / prop / jet engines

[durrell]

Originally Posted by Autospirit

I think some people are imaging that the plane is just supposed to hover up off the treadmill in the same location in which it began. It still need a proper distance to build up speed to generate lift, so this treadmill/runway needs to be long enough. The thrust from a jet engine doesnt care what it is sitting on. Be it 200mph on stable ground or 400mph on a treadmill, as long as the wheels can withstand the rpm's while the plane covers enough distance to generate lift, it makes no difference to the jet engine.

Edit. Pretend the wheels are frictionless. The plan can maintain its location on a 200mph treadmill without even using any kind of thrust. When it does begin to propell itself, it is no different than if it was sitting on stable ground

Exactly. That is exactly the way I see it. The original question I saw said imagine that the treadmill is as long as a runway. So it would still take off, assuming that; regardless of what is going on where the wheels meet the treadmill.

[scuba91ta]

Originally Posted by Mainerunr

correct except that if the wheels and treadmill are moving at the same velocity, opposite direction, then the plane is stationary with respect to the air and thus cannot take off.

WRONG!!!! Just because the treadmill is moving at the same speed the plane is doesn't mean the plane cannot move forward.... The plane will move forward regardless of any counter motion by the ground because the planes interaction with the ground is meaningless...

[Zeek]

Originally Posted by djpain75

Simple guys... without lift the plane isn't going anywhere. If the plane is on a treadmill then the plane really isn't moving is it... only the treadmill is moving, the plane is stationary. Stationary plane = no lift... no lift the plane ain't goin nowhere. Pretty simple

Who cares about the wheels / treadmill / prop / jet engines

You're thinking of a treadmill as if you were running on it. I've got a better idea. Go ahead and read on, but do this right after to test. Build two jet engines out of a couple cabinets, and a oscilating fan, and the sweat of Chuck Norris for fuel (email Mcguyver@Iambetterthanhasslehoff.com if you need the plans). Get on a treadmill, and start it. You're going to have to walk, then run. Now turn on the jet engines, which you're holding out to each side, in your hands. you're going to be pushed forward, and the treadmill will start to move faster, faster than you can run. You're going to fall forward, and probably get sucked through one of the engines.

Maybe that isn't such a good idea.

However, it does illustrate a point. Turning the engines on pushes you forward. It's like someone throwing an anvil at your back....you're going to move forward, and the second you admit that you'd move forward, you have to admit that the plane would take off. It's because, again the only important part of the whole thing is that the treadmill running at 500 mph backwords would not even slow down the engines pushing the plane forward on free spinning wheels.

I think many people picture that, a plane with it's engines running, and a conveyer running in the opposite direction, and they think it would be stationary. The best visual tool is already mentioned here. A room with a treadmill that ran the length of a basketball court. You're standing on a skateboard, ut you have a rope tied to the other (forward) end of the room. You start pulling on the rope, and the treadmill would start moving, making the wheels move beneath you. However, every time you pull in more rope, you do actually move forward. You arms are moving you at say, 2mph, but the wheels are going backwords at 4mph. It'd be easier if the treadmill wasn't going backwords, but the faster you pull forwards, the faster you'll move forwards, no matter what happens with the wheels. that's why there is lift - you - like the plane are acutally moving. The treadmill is just an annoyance.

[westexasrepublic]

i still refer back to my last point.


With the logice and theory of the guys who say it can NOT take off....

if you follow that logic..... then your also basically saying that if the treadmill was going in reverse (same direction as the plane trying to take off) the plane would then magically take off twice as fast!? W W, just aint gonna happen, now quit thinking you are right.

[Inyourface1650]

Originally Posted by westexasrepublic

i still refer back to my last point.


With the logice and theory of the guys who say it can NOT take off....

if you follow that logic..... then your also basically saying that if the treadmill was going in reverse (same direction as the plane trying to take off) the plane would then magically take off twice as fast!? W W, just aint gonna happen, now quit thinking you are right.

hmmmm....how do aircraft carrier catapults work....? Oh thats right, they give the plane air speed without using its own thrust.......same as a forward moving treadmill would, if the plane had its brakes locked....

[fleaofsc]

Holy crap guys we are all saying the exact same thing but in our own way. We all understand that the plane could take off if it wanted too, but if it gives only enough thrust to cancel out friction it is not gonna go anywhere. We are all sitting here arguing with eachother but are all saying the EXACT SAME THING.

[westexasrepublic]

NO we are not saying the same thing. The plan will take off. done. if you think otherwise then you should ask a pilot, or a DR. in physics. THE END.

[Chris M]

It makes no difference whether the treadmill is moving at 1mph or 10,000mph. Sure, the wheels will spin faster, and let's hope the bearings hold up, but it's as simple as this: the jet engines do not rely on the contact between the wheel and the ground. They pull air into the front, and push air out the back, thus moving the plane forward no matter how fast the wheels are spinning. The jets work by moving air through the air. The wheels and ground are irrelevant. Simply think about what propels the plane, and take all other variables out of the scenario, and it'll make more sense to those who think the plane will not take off.



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