hmmm.... physics question for you guys....

[VitaminG]

Re: hmmm.... physics question for you guys....

Alex, the plane isn't thrusting against the ground (or belt), so the speed of the belt is of no consequence.

You put a plane on a surface so slippery that the grip of the tires have no purchase, that won't stop the plane from being pushed forward by it's engines. The wheels' friction with the ground (or belt) has no bearing on its forward drive

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

Okay, nobody said anything about a giant fan or air moving. [img]/images/graemlins/laugh.gif[/img] Wulfe13 never said that in his question. If there is plane movement relative to the air, either caused by the plane moving forward or air moving backward, then Bernoulli's Principle can take place.

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

[ QUOTE ]

You put a plane on a surface so slippery that the grip of the tires have no purchase, that won't stop the plane from being pushed forward by it's engines.

[/ QUOTE ]

True. If you sit a plane on an infinite vat of oil, the plane could move forward and eventually take off, away from that planet of petroleum. [img]/images/graemlins/laugh.gif[/img] But the oil is neutral. The conveyor belt in the original question is working AGAINST the plane and is not neutral. [img]/images/graemlins/tongue.gif[/img]

[VitaminG]

Re: hmmm.... physics question for you guys....

but the same principle applies. The belt isn't working against the primary driving force of the plane. The belt may have an effect on the bearings of the wheels, vibration from the wheels spinning at twice their regular speed (if plane is moving at 300mph, belt moving in opposite direction at 300mph) may cause the undercarriage to shake apart, but I referred to that factor in my first post.

You still haven't satisfactorily explained HOW the belt could possibly keep the plane stationery. Unless you have a wheel driven plane.

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

Yup, I have a wheel-driven plane. [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] Isn't that how planes fly? The treads on the tires grip the air, and planes hop from cloud to cloud when flying? [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img]

The belt isn't working against the primary driving force of the plane (the engines), but the engines are attached to the plane which is attached to the undercarriage. If the plane is on the earth, there has to be a surface under the wheels. And when that surface moves in the reverse direction, a flying plane we will not have.

This is fun! Much more enjoyable than talking about politics, religion, neckthrough VS bolt-on, cosmetics... errrr, scratch that last one. [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/crazy.gif[/img]

[j2379]

Re: hmmm.... physics question for you guys....

the plane would move. a belt would not keep a plane stationary. in a wind tunnel stationary objects with air moving over them at speed will fly or make enough force to.

[Newc]

Re: hmmm.... physics question for you guys....

Because the plane's wheels must turn until the engines build up enough forward thrust to lift. In order to build up enough forward thrust, the plane must have forward momentum and air flow. If the belt under the tires spins at the same opposing rate as the tires, the plane's engines will not push it forward with enough force to lift.

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

See, I had no idea that wind tunnel models actually "floated" there as air passed over them at speeds high enough to sustain "flight". I always thought the models were tethered. Think what would happen when you turn off the giant fan... the model comes crashing down. [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img] [img]/images/graemlins/laugh.gif[/img]

See, it's tethered. [img]/images/graemlins/laugh.gif[/img]

[FusionFarmer]

Re: hmmm.... physics question for you guys....

if the plane ie headed into a 60 mph or better wind it might take off (depending on the aircraft). air speed is the only thing that matters to create lift, thats why planes take off and land into the wind, it helps to create lift. ( ex pilot talkin here)

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

[ QUOTE ]
If the belt under the tires spins at the same opposing rate as the tires, the plane's engines will not push it forward with enough force to lift.

[/ QUOTE ]

See, that was my rationale. [img]/images/graemlins/toast.gif[/img] Very well stated. [img]/images/graemlins/toast.gif[/img]

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

[ QUOTE ]
thats why planes take off and land into the wind, it helps to create lift. ( ex pilot talkin here)

[/ QUOTE ]

Yup, a headwind can reduce the plane's actual speed needed to lift off the ground, as well as shortening the runway distance needed to take off.

[VitaminG]

Re: hmmm.... physics question for you guys....

Newc, your explanation assumes that the wheels are what actually moves the plane forward until the plane gets off the ground, where the engines take over.

The wheels on a plane are like castors, or trundles. The wheels on a child's wagon must turn for it to move forward, but it's the child pushing it that moves it forward, not the wheels.

If the engines are generating enough thrust to push the plane at 300mph, and the belt is moving at 300mph in the opposite direction, the only effect on the wheels (aside from any vibration effects, etc) is that they will spin at 600mph. If for some reason the wheels are physically unable to spin at 600mph, then the conveyor belt analogy might hold some water. But assuming that the wheels can spin at twice the speed of the planes actual thrust, there is no reason why the plane wouldn't move forward on the belt and generate enough lift to get off the ground.

so there [img]/images/graemlins/tongue.gif[/img] [img]/images/graemlins/laugh.gif[/img]

[Carbuff]

Re: hmmm.... physics question for you guys....

So, what about a seaplane trying to take off against a strong water current? I guess it will eventually take off but it will take more thrust and distance to get it off the ground. But I would guess that spinng wheels arent as much of a drag as pontoons on the water surface. I see how it should fly in principle but I dont think its possible to recreate this in real life to see for sure.

[Number Of The Priest]

Re: hmmm.... physics question for you guys....

But again, there's no air moving over the wings. From an observer's standpoint, looking questioningly at an airplane sitting on a conveyor belt of all things, the plane isn't going anywhere on this calm beautiful day. There's no wind, no nothing to push air over the wings. To the bystander, the plane will not just magically float up and off the belt. [img]/images/graemlins/laugh.gif[/img]

[Soap]

Re: hmmm.... physics question for you guys....

hmmm.... physics question for you guys....

Why? You an engineer, or preparing for an apprentice test of some sort, or you high?

Heres one:
My naked bare booty is on the toliet taking a crap.
My booty hole is approx 6 inches from the water resting in the toliet waiting to recieve my turd.
I also, have a 45 hand pistol loaded and ready to fire a bullet to it intended destination. The handgun held firmly in my hand arm fully extended out away from my body, ready to fire. The intended target has a clear unobstacled view permitting a easy successful shot.
The bullet's destination is 20 feet away straight in front of me.

Which will reach the intended destination first?

A.) The turd dangling from my booty hole ready to plunge into the water in the toliet bowl 6 inches away.
B.) The bullet shot from the handgun at the intended target 20 feet away.
C.) Or will they both reach their intended destination at the same time.
[img]/images/graemlins/grin.gif[/img]