Skill's weekend teaser

[fifty2aces]

Skill/Gecko/Other Flat Earthers - Let’s assume your 747 DOES take off under the conditions Skill specifies in post #1.

Do you agree the plane must be travelling at its take off speed for it to actually take off?

Can we agree that in order for the plane to reach take off speed it must have travelled some distance (X) from its starting point at the beginning of the conveyor belt to its take off point. OK with that?

Yes, that's what we've been saying for the last 40 pages. The plane is able to move along the treadmill, and since the wheels can spin freely without exerting a force on the plane, the treadmill doesn't impede the forward motion of the plane.

 

[Skill Leverage]

Flat Earthers... see, this is what gets me riled, when people who are just plain wrong give you attitude. There's no shame in not knowing the answer to something, it's how you respond to education that matters.

 

[MrGecko]

Skill/Gecko/Other Flat Earthers - Let’s assume your 747 DOES take off under the conditions Skill specifies in post #1.

Do you agree the plane must be travelling at its take off speed for it to actually take off?

Can we agree that in order for the plane to reach take off speed it must have travelled some distance (X) from its starting point at the beginning of the conveyor belt to its take off point. OK with that?

I will say that the velocity of the air going over the wings needs to be whatever the threshold is to generate teh lift necessary...

but if we are saying 0 headwind, and you actually need to move the plane through the air to generate the lift, them yeah I'm with you so far.

BUT

the displacement X is relative to the fixed reference frame of the AIR, not the relative reference frame of the conveyor.

Think about a plane on top of the train.. the plane needs to go 180mph w.r.t. the AIR, not 180 w.r.t. the train.

 

[frugi]

*hesitantly, for he already senses the leafy disguise start to fall away underfoot, revealing the treacherous maw of a pit in which freshly sharpened punji sticks lurk at the bottom*

Yes, relative to the stationary bit of the runway down which the strip of conveyor runs, in both cases.

 

[megamuel]

Christ, even I got this after 30 odd pages! The jet engines push the plane through the air until it takes off. The wheels just spin on their axels. The plane moves faster, the runway moves faster in the opposite direction, the wheels spin faster and they keep accelerating towards infinity, or when the plane takes off, and the wheels leave the track. I've put it really simply there. Thats all there is to it...

 

[Skill Leverage]

*hesitantly, for he already senses the leafy disguise start to fall away underfoot, revealing the treacherous maw of a pit in which freshly sharpened punji sticks lurk at the bottom*

Yes, relative to the stationary bit of the runway down which the strip of conveyor runs, in both cases.

Haha mate stick around, if you've got the stomach for it; it's pretty awesome watching as he asks the same question 28 times without acknowledging your responses, or just asks a question entirely irrelevant to the problem at hand...

 

[Skill Leverage]

Also you may need to hold the fort for Team Correct while I'm at the gym... it's pretty straightforward, you just post 'the spinning wheels don't matter' once every ten minutes, or words to that effect.

 

[hwsteele]

I heard that the stimulus package that they just voted in includes over $55million for research about airplanes and treadmills. They say it will create over 700 jobs and save many more.
Now that I know the correct answer I think I will apply for a job with them!
Wait...
On second thought if working there is going to be like reading this thread they can't pay me enough!
Wait...
I just read this thread.


It was still fun though!

 

[TheBramble]

*hesitantly, for he already senses the leafy disguise start to fall away underfoot, revealing the treacherous maw of a pit in which freshly sharpened punji sticks lurk at the bottom*

Yes, relative to the stationary bit of the runway down which the strip of conveyor runs, in both cases.

I just knew YOU would see me coming frugeshilde, but it's too late....they've taken the bait...

 

[TheBramble]

Pons Asinorum

So, we agree the plane has to reach V1 (take off speed) for it to, er, take off.

We agree it has to move a nominal distance (X) from its starting point at the beginning of the conveyor to reach that speed (which is fairly obvious, otherwise an objective observer parallel with the plane's starting position would see it rise without any forward motion, gracefully into the sky).

So, we're all agreed. The plane has to accelerate along the conveyor realtive to a stationary observer at the start point, reach V1 and take off.

All agreed. I'm convinced. You win. But, wait...

....one thing still troubles me.

What was the conveyor doing while the plane was moving from its starting position at the end of the conveyor to point X on the conveyor?

Post 1 requires the conveyor belt and the plane's wheel's motions to match exactly....

...surely for this to still hold true, the conveyor would have moved a distance of X backward. And if this had happened, as it must according to post #1, the net forward motion of the plane is a vector comprised of, hang on a moment, let me double check this, yes, it's +X -X which yields (no, there must be a mistake here somewhere, surely) it yields ZERO. No net movement of the plane at all relative to stationary observer at the end of runway/conveyor.

Hmmmm...guess I'm not so convinced at all, after all.

Good luck with those sailing ships. Watch out for the edge. There be Dragons there...LOL

 

[barjon]

"this is the point that you, and everyone else who got it wrong can't understand - a plane's forward motion has nothing to do with how fast its wheels are spinning."

I didn't say that Skill. While the plane is on the ground its forward motion (or "distance of travel" if you like) is measured by the turn of the wheel. Say the wheel's circumference is 20 feet then the plane will have move forward by 20 feet after one revolution - if the ground underneath the wheel has moved backwards by 20 feet then the plane won't have moved will it?

jon

I concede

Hired myself a 747 for the afternoon and heaved it to the gym treadmill (never could stand pigs).

In my example above I tried it as a consecutive rather than concurrent transaction. First a little burst of power moved the 747 one wheel revolution some 20 feet along the static treadmill. Then I turned on the treadmill - lo and behold the wheels turned backwards but the 747 never moved relative to terra firma even though the wheels finished up on the same spot on the treadmill from whence they started and therefore not moved relative to the treadmill.

ding dong

jon

 

[Skill Leverage]

...surely for this to still hold true, the conveyor would have moved a distance of X backward. And if this had happened, as it must according to post #1, the net forward motion of the plane is a vector comprised of, hang on a moment, let me double check this, yes, it's +X -X which yields (no, there must be a mistake here somewhere, surely) it yields ZERO. No net movement of the plane at all relative to stationary observer at the end of runway/conveyor.

Hmmmm...guess I'm not so convinced at all, after all.

Good luck with those sailing ships. Watch out for the edge. There be Dragons there...LOL

FFS mate, when will you listen?! We have told you about fifty times - THE NET FORWARD MOTION OF THE PLANE IS NOT AFFECTED IN ANY WAY BY THE CONVEYOR BELT

AAAAAAAAAAAAAAAAAAARGH

 

[Skill Leverage]

THE WHEELS ARE JUST SPINNING ON THEIR AXEL... WHY CAN'T YOU BLOODY UNDERSTAND THIS?!

Seriously, a child could understand this. It is now literally you; you are the last person we have to convince of the truth. Apart from perhaps Mr Charts, although I'm pretty sure you are both the same figment of my worst nightmare.

 

[Skill Leverage]

I am off to the gym now; Brambles seriously, enough's enough with the sarcastic banter; you are wrong, and I'm pretty sure even you must know you are wrong by now. I don't think anyone who can operate a computer can be this ignorant to the truth.

If you like you can post another couple of times talking about the wheels spinning imparting a force and the backwards motion of the belt giving a negative vector to the plane; unfortunately for you neither of these things are correct, but you simply cannot wrap your head around the science.

Happy hunting, let me know when the penny drops. SL

 

[TheBramble]

:In my example above I tried it as a consecutive rather than concurrent transaction. First a little burst of power moved the 747 one wheel revolution some 20 feet along the static treadmill. Then I turned on the treadmill - lo and behold the wheels turned backwards but the 747 never moved relative to terra firma even though the wheels finished up on the same spot on the treadmill from whence they started and therefore not moved relative to the treadmill.

Jon, you're doing the same thing as th eothers. You're mixing a dose of reality with what is after all a hypothetical situation.

The treadmill/conveyor is linked (through mechanisms not explained, but specified by Skills) to move precisely and exactly in unison with the wheels of the plane at all times. Period. You've emplyed elayed utliation of the process and inertia which is outside the scope of the theoretical basis of the question.

Judas!

 

[TheBramble]

FFS mate, when will you listen?! We have told you about fifty times - THE NET FORWARD MOTION OF THE PLANE IS NOT AFFECTED IN ANY WAY BY THE CONVEYOR BELT

AAAAAAAAAAAAAAAAAAARGH

I knew you wouldn't read it.

Skills, take a breath and just read without thinking of responding just yet...

Do you still hold that the conveyor is rigged so that it always applies an equal and opposite reaction to that of the wheels of the plane? This was what you state in post #1. Is that still your position or have you changed that without telling me?

 

[MrGecko]

Brambles, I will refer you an earlier post of mine, which contains the premises for the correct solution, and an explanation of why you will never, ever, understand it (unless you are a mathematical linguist or change your perpective).

http://www.trade2win.com/boards/general-trading-chat/54142-skill-s-weekend-teaser-8.html#post671492

Additionally, in respect to your credentials as a Pilot, I refer you to this particular paper:

http://www.apa.org/journals/features/psp7761121.pdf

 

[barjon]

Judas!

Sorry to leave you alone on the treadmill, dear chap, but you're more than capable of spinning the wheels

cheers

jon

 

[TheBramble]

I am off to the gym now;

While you're at the gym sculpting that Adonis-like physique of yours, when you get to the cardio-vascular bit, step on the treadmill.

Set it to whatever speed you're going to be running at or run at whatever speed it's set to - same thing.

When you're comfortable that you're not going to (a) run too fast and pitch over the top of it like an asshole (you're not one btw - but I've seen it done) and (b) not going so slow it throws you off the back like a sack of ****e (you're not one of those either, but I have seen a few of them in my time, here) - when you're in your zone - get one of those little children's flags, you know, the sort that the kids wave at the Queeen as she drives past, and stick it in an orifice of your choosing.

You'll note, once the tears clear from your eyes, that the flag is NOT fluttering. There’s is a really good reason for this. And that reason is that there is no air going past your stationary body (relative to your surroundings).

Only the steady hum of the treadmill beneath your feet totally, completely and exactly matching your forward motion with a backward one of it's own, will remind you of something you never knew. But now, you will. Lucky for you.

It’s only my Benign Compassion for you that has given me the strength to carry on debating this with you. I simply couldn’t allow a brother trader to go through life with erroneous views.

hth

 

[MrGecko]

You'll note, once the tears clear from your eyes, that the flag is NOT fluttering. There’s is a really good reason for this. And that reason is that there is no air going past your stationary body (relative to your surroundings).

If you think this is pertinant to our discussion, I really have given you far too much credit.