OK guys, since I'm a Mod I'll bow out and leave it at this;

According to this direct quote from the very first post in this thread:

"A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). "

This tells us the conveyor belt moves under the plane to exactly match the forward velocity the plane would normally have if it weren't for the conveyor belt.
So, by the rules of this game, the plane NEVER realizes any forward velocity.
It doesn't matter if the converyor belt is 5000 miles long, the plane never moves forward - that's what the rules of the question establish.
You can't change them so that the plane "outruns" the conveyor belt and still manages to achive forward velocity.
The rules prohibit that. The rules state the plane never moves forward because it sits on a system that exactly matches what would normally be its velocity so that the plane remains stationary.

In fact the wording of the premise is wrong. The conveyor control system couldn't "track the planes speed" because the plane would have no speed (by the rules attempting to be established). We understand what the question is TRYING to state, but it is technically inaccurate.
A more accurate reading would be:
"The plane sits on a conveyor belt with a control system that varies the velocity of the belt system underneath the airplane so that no change in engine thrust results in forward movement of the plane."

The plane is, in essence, "treading water". It can generate maximum thrust, but all attempts to move forward are exactly offset with the belt system so that the plane never moves.

So, how can it fly if it never moves forward?

Answer. It can't.

With that, I'll bow out and leave the discussion to others.

Thanks for the discussion.

 

He's only human..................

 

Absolutely astonishing. I have no idea how you can let a concept like this fly right over your head.

LOL... no pun intended.

 

The comments such as the "treading water..." one are hilarious .....
But where's the Snoman to straighten us out? Or torque1st?

 

You guy's must be kidding me.

I thought this discussion was done yesterday?

I wish we could add a poll to this thread---fly or no fly.

My vote---fly. For the reasons I said yesterday---which I still stick to.

STan

 

Nah, I'll bet we can keep it going for at least another 5-6 pages ----if not we'll put a treadmill under it. That'll keep it going ..........

 

I'm back.....
And now I see the point of contention.
It all is how you read the initial premise.
Read the way I read it, so that some conveyor is capable of keeping the plane stationary, the plane will never lift off.

But, after much (and I do mean MUCH) study, I now understand the way you guys are reading it.

And, in that light, I AGREE !!

If your treadmill allows the plane to achieve forward velocity and matches AIRSPEED with a counter acting GROUNDSPEED as seen on the treadmill, then yes the plane will fly, because it is free to achieve whatever airspeed it wants, the wheels are simply spinning faster than they would on a fixed runway.

If the conveyor is such that is offsets the airplane's GROUNDSPEED with an equal and oppostie GROUNDSPEED, the plan would sit motionless and never take off.
So if the plane tried to move forward (relative to the ground) at 10 mph, the conveyor belt would automatically adjust and run 10 mph in the opposite direction so that the plane never moved.


groundspeed / airspeed : THAT DISTINCTION is the key to understanding it all.

The initial premise mentions "SPEED", but does not specify groundspeed or airspeed. It makes a difference, at least it did to me.

There now, am I such a bad Moderator after all?

 

EXAAAACTLY!!! That's the whole reason for posing a question this way... to make you think about things differently than you would normally. And a discussion like this one is a great way to bring in all kinds of differing veiwpoints.

 

Well, at least you can admit you were wrong, and that makes you a good moderator in my book.



STan

 

Amen! And Merry Christmas to all . . . And to all a good night.

 

Ouch! I just spent 3 hours in chat at another site and only 3 out of 10 people got it. My head hurts from this and I just found it today. Evil thread!

 

BWAH-HAH-HAHHH!!!

The only issue here is what the aircrafts tires are speed rated at. If I remember right, a 747 will rotate and lift at about 120 MPH.

If the conveyor runway (Now theres a phrase for ya...) matches the aircrafts FORWARD MOTION equally and oppositely - those tires will be turning at the rate they would be if the aircraft were on the ground travelling at 240 MPH.

Consider - for the runway to move, the aircraft has to move. The aircraft will move in relation to the surrounding air and geography, count on it. The runway's only effect will be to put unecessary wear on the tires (if they don't blow up and cause a crash).

I'm glad I saved this thread for a slow night

ONEDIT: Yup - I figured the answer was somewhere in the other posts I skipped. I just went back and looked for it.

 

If the tires blow, and the plane crashes, will it skid down the runway or crash without moving???

 

Reference the airspeed of the swallow - is it African or European?

 

Well, they shut the local coal mine down. I just bought the entire conveyor system! Now, I need a airplane, one that will fly or not fly, I'm not sure? Anyhow, I need a plane for my conveyor! I just want my head to quit hurting!