Mythbusters - airplane on a conveyor belt

Tre1nt wrote:

Conveyer belts move (or convey) things.

Treadmills keep the user (usually a runner) in place.

It's not just semantics. If the plane stays in place it does not fly. If it moves forward relative to the ground AND air it might fly.

haha i've never seen someone take this angle. "A" for originality.

Air moving over wing + thrust = flight

No air moving over wing + thrust = no flight.

Final note: Planes and rockets are not the same thing.

Tre1nt wrote:

Conveyer belts move (or convey) things.

Treadmills keep the user (usually a runner) in place.

It's not just semantics. If the plane stays in place it does not fly. If it moves forward relative to the ground AND air it might fly.

How can a treadmill keep a plane in place? What interaction does the treadmill have with the cause of thrust for a plane? The thrust of a plane being the action of the props or jet on the air. There is no connection between the treadmill and the air - therefore a treadmill could never keep a plane stationary.

Tre1nt wrote:

Air moving over wing + thrust = flight

No air moving over wing + thrust = no flight.

That's great - But, you still aren't answering the question - how can a treadmill keep an airplane from moving?

Neb wrote:

Tre1nt wrote:

Conveyer belts move (or convey) things.

Treadmills keep the user (usually a runner) in place.

It's not just semantics. If the plane stays in place it does not fly. If it moves forward relative to the ground AND air it might fly.

How can a treadmill keep a plane in place? What interaction does the treadmill have with the cause of thrust for a plane? The thrust of a plane being the action of the props or jet on the air. There is no connection between the treadmill and the air - therefore a treadmill could never keep a plane stationary.

i wouldn't bother, if he can't see that treadmills and conveyor belts are fundamentally the same(minus the hand rails of course) , he has no chance at the actual riddle.

If you allow the plane to move forward in your hypothetical then it will fly.

If someone else presupposes that the hypothetical involves a treadmill that negates the thrust it will not fly.

In a real-world situation ... why would anyone bother with a real-world experiment? We know planes fly.

This is too easy.

What if you rig it so the throttle controls the speed of the conveyor belt as well as the airplane engines? No flight!

In a real world situation I don't think you can do that. Engines will turn on, plane will move forward, plane will fly.

Alan

To people that think it won't fly:

How does the airplane move once its left the runway? After all, the wheels are no longer in contact with the ground! How does it move forward?! Scary stuff.

Agreed ... the plane will fly in any real-world experiment. It will be a long taekoff, however.

Runningart2004 wrote:

What if you rig it so the throttle controls the speed of the conveyor belt as well as the airplane engines? No flight!

Alan

Would you also rig the giant treadmill with a mechanism for throwing extra fine particles of sand into the airplane wheels bearings? Or perhaps a giant vacuum to counter the thrust of the planes engines? Then you might just be right. No flight!

Runningart2004 wrote:

What if you rig it so the throttle controls the speed of the conveyor belt as well as the airplane engines? No flight!

In a real world situation I don't think you can do that. Engines will turn on, plane will move forward, plane will fly.

Alan

Alan - what does "speed" of the airplane engines even mean?the FORCE of the conveyer belt on the plane has to match the FORCE of the engine on the air in order to keep the plane stationary.

Big Ten Engineering wrote:

http://youtube.com/watch?v=-EopVDgSPAk

this needs to be watched by the naysayers. I will continually quote/post this link until you ignorant people SHUT THE F*CK UP. Learn things.

Right! Which is why in the hypothetical "treadmill" situation the plane does not fly.

Whereas posing this with "a conveyer belt as long as a normal runway" obviously sets up a hypothetical where the plane taxis -- albeit weirdly slowly at first -- along the runway/conveyer belt until it either 1) reaches a speed sufficient for takeoff, or 2) fails to take off because the moving runway negates the thrust.

Tre1nt wrote:

Agreed ... the plane will fly in any real-world experiment. It will be a long taekoff, however.

Why is the takeoff any longer than normal?

Tre1nt wrote:

Right! Which is why in the hypothetical "treadmill" situation the plane does not fly.

Whereas posing this with "a conveyer belt as long as a normal runway" obviously sets up a hypothetical where the plane taxis -- albeit weirdly slowly at first -- along the runway/conveyer belt until it either 1) reaches a speed sufficient for takeoff, or 2) fails to take off because the moving runway negates the thrust.

What post are you replying to?

Tre1nt wrote:2) fails to take off because the moving runway negates the thrust.

Are you F*cking SERIOUS Neb?

You're gonna bash me, my school, and my opinion because over a stupid science riddle like this?

After returning from my run (we discuss that topic here too), I noticed the need for a lot of Ohio State fans to bash my post. Excuse me if I think my degree might give me a slight edge to make a reasoned opinion, over a redneck osu fan.

There is a reason why this "arrogant, stupid, know-nothing" engineering student writes his email down along with his name- If you're gonna bash me over a disagreement, send me an email. Dont do it on this thread. This is why I hate posing on these boards, because assholes like Neb and Big Ten Engineering have to smear sh*t opionions over every post.

The fact you looked up my personal information is just pathetic. You couldnt keep the thread going? You had to put up my personal info? and what did that get you?

You found out Im from Columbus, but went to Michigan. Great Job.

Please, really, go F*ck yourselves.

Anyway,

The question is broken, it seems to me. It says the speed of the belt matches that of the plane, whatever that means, but also implies that the plane is kept in its starting position.

There are 2 completely different ways people are seeing this.

After thinking about it for a while, Ive changed my mind... a bit.

When the plane starts rolling forward at 1 MPH, how fast does the conveyor belt move? 1 MPH the opposite direction? That means the wheels of the place are rolling at 2 MPH but the plane's overall speed is not affected, except maybe by the added friction in the wheels. The plane could just match the velocity of the treadmill, but then NOT take off.

If the thrust keeps increasing, the plane accelerates, and assuming the wheels can withstand moving over twice their normal maximum rate of rotation, it actually might take off.

Its still about air flowing over the wings. In this case, the plane moving down "the super-long (runway sized) treadmill" might see enough airflow to actually lift off.

Honestly, this is going to keep going unless we see a video of a plane on a treadmill.

Of course it would take off. Otherwise, assuming that the treadmill and the wheel are in perfect synch with each other (no sliding), you'd have to come to a conclusion that the rolling friction of the wheel would be equal to that of the thrust of a jet engine. As an engineer, what do you think of that?