conveyor belt and plane answered at last ??

[crank39]

This is the original question....

An aircraft is standing on a very long runway that can move (a conveyor belt). The aircraft moves in one direction, while the conveyor belt moves in the opposite direction. This conveyor belt has a control system that tracks the aircraft's wheels speed and tunes the speed of the conveyor belt to be exactly the same as the wheels, but in the opposite direction. There is no wind. The pilot begins to add thrust to the engines...

Will the plane ever take off?

I haven't lost the argument, just answer the question above, will the plane leave the ground or not.

It doesn't matter if it's nonsense, irrelevant or just plain stupid. yes or no.

Hi all
Right had a quick scan through and thaough I'd give my thoughts, and I"m on the side of joe90 and co
Sorry doitall but Based on the question in that context then yes realistically the plane will take off
You are presuming that the belt can hold the plane stationary in relation to the air around it which it, can't, you are also presuming that the planes wheels are going to be stationary which they are not, the belt would have to be rotating in the same direction as the wheels for that to happen ( which still wouldn't stop the plane taking off)
As others have said, the Plane is being subjected to forward thrust from its engine/prop
It's wheels are freewheeling they will spin faster but the plane will still take off no probs when its airspeed reaches takeoff velocity

With all due respect you have not thought through any thing of what you've just written

 

[Deleted member 63160]

How do you measure the speed of the conveyor or the wheels? Wheels say RPM, treadmill RPM? You'd have to really as the plane aint moving so neithers the treadmill. Both turning but not moving back or forth. Tread mill at least the length between the planes wheels say 60 ft so the belt maybe 160ft total for instance. Circumference of plane tyre say 20 ft. Plane wheels are spinning 8 times as fast already to keep the plane staionary. Only jokin

 

[matt1e]

Ok crank no offence taken
which bit of my post is confusing you?
And yes well put MW

Matt

 

[doitall]

The wheels are free wheeling only being driven by the belt, therefore if the plane is stationary the wheels and the belt must be the same speed, no different to the treadmill.

The person on the belt will have to walk/run the same speed as the belt. Give the person skates or a go cart and he/she still has to match the belt speed or go backward or forward if he goes faster.

 

[crank39]

which bit of my post is confusing you?

All of it really

Its been explained so many times and i'd just be repeating what i and a few others have said already, i thought with MW's post the penny would drop, it was so close, read it again slowly and compare it to what you think or thought would happen, but heres a pointer...

Belt going backwards at 100mph must mean wheels turn forward at 100mph.........AGREED?

If you agree with the above then you MUST agree that the plane is currently stationary................AGREED?

For the plane to move forward up the conveyor and hopefully to take of speed it needs to increase thrust..............AGREED?

No one is disputing that the plane has plenty of thrust in reserve to overcome the conveyor going backwards

BUT here's the clincher, in order for the plane to move forward up the conveyor the wheels will need to travel faster than they already are, remember they are already travelling at 100 mph because the conveyor is too.....................PLEASE SAY YOU AGREE

As soon as the plane moves forward, which it could easily do with extra thrust the wheels are NO LONGER travelling at the same speed as the conveyor and that is not within the parameters of the question, if the wheel speed is equal to the conveyor then the plane will stand still and will not take off because of no air flow over the wing surfaces

 

[joe-90]

The question is nonsense. What you need to ask yourself is "Did the guy that wrote it mean it to be complete nonsense?"

I don't think he did. He meant stick it on a rolling runway and see if it takes off. The answer to that is YES.

 

[crank39]

The question is nonsense. What you need to ask yourself is "Did the guy that wrote it mean it to be complete nonsense?"

I don't think he did. He meant stick it on a rolling runway and see if it takes off. The answer to that is YES.

So you concede that if it stays within the parameters of the question then the plane will not take off?

 

[joe-90]

The question doiesn't make sense within the constraints of the laws of our universe. The question is flawed.

 

[crank39]

You mean it doesn't suit what you thought would happen

 

[joe-90]

No. I mean it makes no sense. The question assumes the plane and conveyor to be moving - but if they are both moving then the question is void.

 

[Trazor]

For all those, it won't take off merchants, consider this.......

According to you lot an aeroplane coming into LAND on this conveyor belt would have to stop INSTANTLY the moment it touched down, as you believe the conveyor stops forward movement.

Thats 400 metric tonnes stopped instantly( boeing 747 )

This is obvious nonsense.

 

[Norcon]

crank39 wrote

Belt going backwards at 100mph must mean wheels turn forward at 100mph.........AGREED?

Nope.

How does a wheel "turn" forward at 100mph?

 

[crank39]

crank39 wrote

Belt going backwards at 100mph must mean wheels turn forward at 100mph.........AGREED?

Nope.

How does a wheel "turn" forward at 100mph?

D'errr, conveyor travels one way means wheels turn the opposite way, but we've gone past this point, does this not happen on your planet?

 

[crank39]

For all those, it won't take off merchants, consider this.......

According to you lot an aeroplane coming into LAND on this conveyor belt would have to stop INSTANTLY the moment it touched down, as you believe the conveyor stops forward movement.

Thats 400 metric tonnes stopped instantly( boeing 747 )

This is obvious nonsense.

Not instantly but eventually yes, remember the 747 has forward momentum , the wheels currently stationary, when it touches down on the conveyor, which is travelling backwards the wheels will spin forward at 100mph + whatever the touchdown speed of said plane was

When the forward momentum clearly slows and the wheel speed matches the conveor speed the 747 will stand still, if it slows then it'll go backwards

 

[Norcon]

crank39 wrote

Belt going backwards at 100mph must mean wheels turn forward at 100mph.........AGREED?

Nope.

How does a wheel "turn" forward at 100mph?

D'errr, conveyor travels one way means wheels turn the opposite way, but we've gone past this point, does this not happen on your planet?

Nope.
That doesn't answer the question. Only adds confusion as you've mentioned a "conveyor" which has nothing to do with the question I was asking.

So once again ..how does a wheel "turn" forward" at 100mph? Just answer the question. (he won't)

Define what exactly is "turning" and what exactly is moving "forward" from your statement above.