Would the plane take off?

[bofh]

i dont see how you guys think it can lift off, unless i'm missing something major.

Yeah, you're missing that a plane doesn't use the ground to accelerate.

To cite an example above, an icy runway doesn't effect the takeoff distance.

[Army]

if its already in motion, as in flying, when it comes over the conveyer belt, then sure, it can take off because it will have speed, and lift.

whereas i think the question is stating that the plane and conveyor belt are both at a stop, and both start and accelerate at the same time, thus not moving it anywhere.

i dont see how you guys think it can lift off, unless i'm missing something major.

The 747 does NOT rely on its wheels for forwrd motion---they are unpowered. The jet's engines push it forward, unheeded by the conveyor or wheel speed. When the 747 reaches flight speed, it will, regardless of the speed or direction of the belt and wheels.

[Army]

with a propeller driven plane, i could see it taking off, as the propeller is directly pushing air over the wings.
where as on a jet, it is sucking air in under the wings, and pushing it out really fast behind the plane. i dont think it gives it lift.

Propellers pull, jets push. The wind they generate is only for forward motion, NOT supplying airflow over or under the wings. Forward motion will provide that.

[wanna-b-ballin']

This sounds like the best way to explain that the runway surface friction/direction doesn't really do a damn thing in the take off of the plane.

The plane flies.

uugh. for the plane to get lift it has to be moving forward. the wheels do not make it go forward, they just let the plane roll with the force created by the jet. on ice, the jet will roll forward.
on the conveyer, it will not because the "land" it is on is going the opposite direction, thus preventing the plane from being able to move forward.

i really can't explain it more.

[Bear_Claw]

Yes the plane would accelerate but the tires would blow out due too excessive speed and the plane would crash their for not taking off.

Nope i aint no enginer either im a mehcanic LOL

[wanna-b-ballin']

damnit, now i have to go try this crap. i'm starting to understand armys point, but i just can't bring myself to completely understand how the jet would go forward.

i dont have a treadmill, but my friend does.

i have a remote controll airplane, propeller driven.

i think it will simulate it well enough if i put the two together. but i think his parents would be a little pissed if it did take off, as they have too much expensive fragile crap in that room.

i'll ask his dad that question though, he is a pilot, and is very good at comprehending that sort of difficult/should-be-easy sort of stuff.

[billybob_81067]

uugh. for the plane to get lift it has to be moving forward. the wheels do not make it go forward, they just let the plane roll with the force created by the jet. on ice, the jet will roll forward.
on the conveyer, it will not because the "land" it is on is going the opposite direction, thus preventing the plane from being able to move forward.

i really can't explain it more.

The thrust pushing the plane forward pushes off of the AIR BEHIND THE JET ENGINES, NOT THE GROUND/CONVEYOR BELT... Therefore unless the conveyor belt could move the air above it the jet will still take off...


Hmmm... even if the conveyor could move the air, that air movement would then make lift due to it passing over the wings.

[wanna-b-ballin']

why are people thinking i'm saying the wheels are powered. i know they arent. they just allow the plane to move easier than if it were just dragging its *** across the ground. they help with the friction.


the plane has to be moving forward at a high enough speed to create lift with its wings. with the conveyor moving the opposite direction, the plane cannot move forward. yes, it will be accelerating, and the jet pushing harder and harder, yet so will the conveyer belt. so the plane will not be able to take off.

someone mentioned the rocket thing. so how is the plane going to all of a sudden have enough thrust to take off like a rocket?

[billybob_81067]

why are people thinking i'm saying the wheels are powered. i know they arent. they just allow the plane to move easier than if it were just dragging its *** across the ground. they help with the friction.


the plane has to be moving forward at a high enough speed to create lift with its wings. with the conveyor moving the opposite direction, the plane cannot move forward. yes, it will be accelerating, and the jet pushing harder and harder, yet so will the conveyer belt. so the plane will not be able to take off.

someone mentioned the rocket thing. so how is the plane going to all of a sudden have enough thrust to take off like a rocket?

But the air that the jet engines push against with their thrust is not moving backwards with the conveyor belt...

The wheels would spin like crazy, yet the jet would still push forward.

Think of it this way. Say you're running on a threadmill at 15 mph, and someone turns a fan on behind you. You can feel that air right? That's cause the conveyor/treadmill has NO effect on the air.

Or say you've got a skateboard on one of those conveyor walkways at the airport. if you just stand there on it then the backwards motion of the conveyor cancells out the forward motion of the skateboard. But now run a rope tied to a pole at the end of the conveyor and you can pull yourself through the conveyor walkway no matter if it's going 5 or 100 mph, because the conveyor has no effect on the rope.

[bleachit]

"So far the J-3 has not moved, nor has the conveyor. At idle power, there's not enough thrust to move the J-3 forward on a level surface, so Manfred starts to bring up the power, intending to take off. The propeller rpm increases and the prop shoves air aft, as it does on every takeoff, causing the airplane to move forward through the air, and as a consequence, forward with regard to the ground. Simultaneously the conveyor creaks to life, moving east, under the tires of the J-3. As the J-3 thrusts its way through the air, driven by its propeller, the airspeed indicator comes off the peg at about 10 mph. At that moment the conveyor is moving at 10 mph to the east and the tires are whirling around at 20 mph because the prop has pulled it to an airspeed, and groundspeed, of 10 mph, westbound. The airplane is moving relative to the still air and the ground at 10 mph, but with regard to the conveyor, which is going the other way at 10 mph, the relative speed is 20 mph.

Manfred relaxes a bit because the conveyor cannot stop him from moving forward. There is nothing on the airplane that pushes against the ground or the conveyor in order for it to accelerate; as Karen -- one of our techies here at the Lounge -- put it, the airplane freewheels. In technical terms, there is some bearing drag on the wheels, but it's under 40 pounds, and the engine has overcome that for years; plus the drag doesn't increase significantly as the wheel speed increases. Unless Manfred applies the brakes, the conveyor cannot affect the rate at which the airplane accelerates.

A few moments later, the roaring Continental, spinning that wooden Sensenich prop, has accelerated the J-3 and Manfred to 25 mph indicated airspeed. He and the airplane are cruising past the cheering spectators at 25 mph, while the conveyor has accelerated to 25 mph eastbound, yet it still has no way of stopping the airplane's movement through the air. The wheels are spinning at 50 mph, so the noise level is a little high, but otherwise, the J-3 is making a normal, calm-wind takeoff.

As the indicated airspeed passes 45 mph, groundspeed -- you know, relative to where all those spectators are standing beside the conveyor belt -- is also 45 mph. (At least that's what it says on Manfred's GPS. Being brought back to life seemed to create an insatiable desire for electronic stuff.) The conveyor is also at 45 mph, and the wheels are whizzing around at 90 -- the groundspeed plus the speed of the conveyor in the opposite direction.

Manfred breaks ground, climbs a few hundred feet, then makes a low pass to see if he can terrify the spectators because they are Americans, descendants of those who defeated his countrymen back in 1918. "

thats from the link a while ago, as there still seems to be some who dispute the ability to fly. I think that says it rather clearly.

[anomoly40]

Just watch this.

http://media.putfile.com/Plane-runway-conveyor

If this helps.
Imagine someone sitting on a skateboard. Now imagine that skateboard is on a tread mill. Now imagine that the person is holding a rope that is tied to a wall. Now no matter how fast that treadmill spins the person isn't using the wheels to hold theirself in place, they're using the rope. Now if they pull the rope they move foward no matter how fast the treadmill is going.

The person on a skateboard is the Jet.
The treadmill is the conveyor.
The rope is the surrounding air.
The person pulling on the rope is showing how the jet pulls the air to move.

[Pacifist_Farmer]

^

He Wins, it flies, thats that

[Lohman446]

If the jets are creating forward movement the wheels of 100MPH and the treadmill is making that remain stationary to the non-mobile ground around it the plane will not take off.

Regardless of the amount of thrust from the engines it is not the engine thrust over the wings on most aircraft that create lift. It is the movement of air over the wings. Because the plane is stationary to the stable ground and air around it there is not the required movement of air over and under the wings to create lift.


"But the thrust of the jet" - nonsense. Planes glide without engine power, in fact there are some that are designed to not have an engine. Take a 747 and disable the engines while in flight. It will still "fly" though not gain altitude once it falls below a certain speed.

Air speed causes lift, not some manufactured ground speed. If all one needed to lift off was the thrust of the jet engine then we would not use wheels for take off, the plane would simply sit, locked to the ground (wheels chocked for instance) and lift off without a runway.

[rkjunior303]

The only thing you haven't explained is exactly how you're going to overcome physics. The problem says that no matter HOW FAST your wheels are spinning-- freewheeling-- the conveyor is going toexactly match that speed. I'm not convinced I'm right-- but no one has explained how exactly this plane is going to overcome 0 net movement.

I think this problem is dependent on the fact that these wheels would be completely frictionless, which would then allow them to spin freely at any speed.

[tropical_fishy]

I think this problem is dependent on the fact that these wheels would be completely frictionless, which would then allow them to spin freely at any speed.

Yeah, I got it, bill explained it to me last night.