A plane on a conveyor belt

[loopstah]

An excellent explanation. I think this vid complements it perfectly

http://youtube.com/watch?v=bEyfHwDdXSg&feature=related

If anyone still fails to understand what's going on after watching that then there's no hope for you.

 

[andyp]

Just accept that you are completely wrong and stop trying to avoid that fact by saying "its a pointless question anyway".

You sir are totally the guy at school who gets an F in science and says "I didnt want a good grade anyway"

I didn't take science.

I took seperate biology, physics and chemistry. And I achieved my estimated grades on each subject.

However that's irrelevant, and it happened over 10 years ago.

But I see you point, and you are mistaken - I don't understand what I'm 'wrong' about.

 

[The Dread Pirate]

But can you swim uphill?

Don't start this again

 

[MTA99]

Since people are wondering how to define the problem, I will offer one. Inherent in the concept behind the question is that the treadmill is there to stop forward momentum. If the plane could move on the treadmill, relative to the ground, then there would be no point in setting the question to begin with - this is how planes normally take off (incidentally assuming the hypothetical treadmill was able to keep up with the plane, I do not see how any absolute forward momentum would be possible).

The highlighted sentence is an assumption you make about the problem. It is this assumption that catches out the nay-sayers. As you continue to explain the treadmill is irrelevant.

 

[KPeh]

Fair enough .

 

[hamesy]

If the plane is facing in the opposite direction of the conveyor belt then even it's its wheels aren't powered and it starts to pick up speed, it will be facing the wrong way. Planes aren't designed to tale off backwards!

I think you've got the wrong end of the stick. The plane faces one way, and the conveyor belt moves in the opposite direction. Plus the wheels don't provide the forward motion.

 

[Helium_Junkie]

Of course it can take off.

But can you swim uphill?

Guys, stop being so rude - seriously. There's no need for the insults being flung around. "God theres a lot of thickos here!" for example - completely uncalled for.
If you can't prove your point in a civilised fashion, perhaps you should leave it for others who can, will and have.

 

[Peter Diffey]

If the plane is facing in the opposite direction of the conveyor belt then even it's its wheels aren't powered and it starts to pick up speed, it will be facing the wrong way. Planes aren't designed to take off backwards!?

Friction in the wheels is negligable

 

[andyp]

now you have me completely confused why do the planes need to travel at 180MPH to lift off? I would have thought that was to do with lift and not power produced by the engines.

Thrust from the engines propels the plane forwards. As the air rushing over the underside and topside of the wings creates a pressure difference, eventually when the plane reaches a certain speed the difference in pressure will enable the plane to leave the ground. Essentially the whole weight of the plane is transferred from the wheels to the wings. Watch any take-off in humid conditions and the split-second the wheels leave the ground you'll see condensation streaming from the wingtips and trailing edges. That's the point where the lift is enough for the wings to take the weight of the plane.

 

[semi-pro waster]

But a lot of the original question has nothing at all to do with an aircraft taking off.

So it's swings and roundabouts.

But the point of the original question is for you (anyone) to determine the factors in the equation that could safely be taken out as irrelevant. In your question there are three factors you have introduced that cannot be ignored in this fashion (weight, drag/aerodynamic issues and that there aren't enough chimps in the World) so no, I can't agree it is swings and roundabouts because you are comparing fundamentally different things.

 

[Mulder]

Friction in the wheels is negligable

So the question really is what powers the initial movement of the plane? If the wheels do it won't be able to take off as the conveyor belt would prevent it from starting the momentum required to get any lift. If the engined provide the initial momentum however then the conveyor belt is irrelevant. Am I right?

 

[Blue Cypher]

There is no air pressure on the wings to create upward draft (the engines just move it forward, nothing else) so if there is no pressure on the wings then there is no upward draft meaning it wont take off. so for all the people who said it would take off can you give me an explanation please as i cant see how it would.

 

[ramdor]

It'll take off, but it will need ever so slightly more thrust than normal.

As far as I can see...

1) If the wheels had zero friction and there was zero thrust the plane wouldnt move. The wheels would spin only.

2) If the wheels have some friction and zero thrust, the plane would move backwards (accelerating). The wheels would spin at first but eventually they would stop when the the plane was moving backwards at the speed of the belt.

3) If the wheels have friction and the plane has thrust greater than that needed to counter the friction/backwards movement in (2) then the plane would move forward, creating lift over the wings and taking off.

For the plane not to move, the belt would have to move as some stupid mph (like millions??) so to create so much friction/backwards drag through the 'free wheeling' wheels.

Richie.

 

[Belmit]

That sentence is stupid if the conveyor belt is moving at the same speed as the plane the planes wheels will be turning on the stop. Try running at 5.5 MPH on a treadmill that's set to 5.5 MPH see how far you move. Feel the wind beneath your wings. LOL

That's not analogous because you're generating the forward momentum through your legs. If you were standing still wearing roller skates on a moving treadmill though, you'd be closer. And more amusing to look at.

 

[Toothpick]

Plane engines/propeller provides the forward thrust - ergo the wheels and by extension the treadmill are irrelevant.

And thats why people get confused. The question will misslead anyone who does not have a high command of the english language.

"Will a plane with no wheels take off on a friction-less runway? "

thats a clearer (well maybe) form of the original question, with out the missleading guff.

 

[Peter Diffey]

So the question really is what powers the initial movement of the plane? If the wheels do it won't be able to take off as the conveyor belt would prevent it from starting the momentum required to get any lift. If the engined provide the initial momentum however then the conveyor belt is irrelevant. Am I right?

Yep thats correct, thats the intelligent leap that you have to make - to realise that its accelation is due to the force provided by the prop engine(s) and nothing to do with the wheels on the ground

 

[jas72]

Dude, have you read any of the other pages?

The plane is moving forwards from the trust from the engines, the plane doesn't move by using the wheels.

take the wheels off and the plane would move forwards as there is no ground speed however since the plane is attached to the ground it's wheels are responsable for traction which eventually gives lift which keeps the plane off the ground. However whilst it's on the ground the plane requires traction the wheels are not providing any thus it doesn't move. No matter how powerful the engines are.

 

[andyp]

And thats why people get confused. The question will misslead anyone who does not have a high command of the english language.

"Will a plane with no wheels take off on a friction-less runway? "

thats a clearer (well maybe) form of the original question, with out the missleading guff.

It will also mislead anyone who doesn't like to overcomplicate matters for the sake of it to appear 'cleverer' than everyone else.

 

[p4radox]

So the question really is what powers the initial movement of the plane? If the wheels do it won't be able to take off as the conveyor belt would prevent it from starting the momentum required to get any lift. If the engined provide the initial momentum however then the conveyor belt is irrelevant. Am I right?

Yes, as long as the increased friction from the wheels spinning at a much higher rate is neglected.

I think an interesting problem would be if you had a plane with skiis (rather than wheels) in a water bath. Obviously in stationary water the plane would take off with ease. But if the water bath were a "treadmill" water bath with a surface current opposing forward motion, would the increased friction on the skiis prevent the plane taking off?

For added confusion, could the plane take off in an "uphill" water bath?

 

[Mat]

it's wheels are responsable for traction which eventually gives lift which keeps the plane off the ground. However whilst it's on the ground the plane requires traction the wheels are not providing any thus it doesn't move. No matter how powerful the engines are.

What?! That makes no sense at all...