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☖ Forums → Discussion Forum → Airplane on a conveyor belt
123456
Airplane on a conveyor belt
2007-03-09, 8:30 PM #1
An airplane is sitting, landing gear down, on the middle of a huge conveyor belt. The belt is programmed such that it travels backwards at the same speed the plane moves forwards. The planes engines are started and throttle up to full power. Does the plane take off?
Stuff
2007-03-09, 8:31 PM #2
no lift would be created? :confused:
Welcome to the douchebag club. We'd give you some cookies, but some douche ate all of them. -Rob
2007-03-09, 8:39 PM #3
Heh...you'll have some fast-moving wheels...but she'll fly.
woot!
2007-03-09, 8:49 PM #4
UNGLAUBLICH
2007-03-09, 8:51 PM #5
crap, I hit no by mistake.

Dammit.
SnailIracing:n(500tpostshpereline)pants
-----------------------------@%
2007-03-09, 8:52 PM #6
Yes. The plane's engines act on the air, not on the ground.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2007-03-09, 8:52 PM #7
The universe would explode.

o.0
2007-03-09, 8:57 PM #8
Oh. I get it now.
I had a blog. It sucked.
2007-03-09, 9:02 PM #9
Man, we've had these before. Aren't there any new ones?
2007-03-09, 9:32 PM #10
I remember this question the last time we had it. I think I argued for about four pages before I finally "got it."

Physics never was my strong point.
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2007-03-09, 9:34 PM #11
Unless the brakes are on. It'll fly.
2007-03-09, 9:40 PM #12
...without forward motion the wings cannot produce lift.
omnia mea mecum porto
2007-03-09, 9:42 PM #13
I agree with Roach. The engines create thrust, which moves the plane forward. It's the forward motion that moves air over the wings that creates the lift.
Pissed Off?
2007-03-09, 9:42 PM #14
Aw, Roach, you disappoint! ;)

The wheels are not driven on a plane. They can spin in any direction and the plane will still take off. They are only there to keep the plane off the ground.

Think of it this way...if a plane were to have its landing gear down mid-air, would spinning its wheels backwards make it go slower?
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2007-03-09, 9:50 PM #15
The wheels down would make the plane go slower if it were flying, but that would be because of drag.
Pissed Off?
2007-03-09, 9:50 PM #16
Right right.

(Unless the landing gear weren't rated for twice the take-off speed of the aircraft ;) )

Good thing I didn't vote yet...now I'm free to cheat :ninja:
omnia mea mecum porto
2007-03-09, 10:00 PM #17
Originally posted by Avenger:
The wheels down would make the plane go slower if it were flying, but that would be because of drag.


Please tell me where in the original description it says that the plane isn't moving forward. Because it is.
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2007-03-09, 10:05 PM #18
Free, I don't think he was implying anything in that statement, so stop trying to be snarky. ;)
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2007-03-09, 10:07 PM #19
The plane is moving forward, but only on the conveyor belt, which is traveling in the opposite direction at the same speed. Since the conveyor belt is not moving the air, there would not be enough lift to take off.
I can't wait for the day schools get the money they need, and the military has to hold bake sales to afford bombs.
2007-03-09, 10:11 PM #20
Net speed = 0
Pissed Off?
2007-03-09, 10:11 PM #21
Originally posted by Avenger:
Net speed = 0


Wrong. Net speed is nearly what it would be on a normal runway.
"it is time to get a credit card to complete my financial independance" — Tibby, Aug. 2009
2007-03-09, 10:17 PM #22
[Edit - Actually, nevermind]
omnia mea mecum porto
2007-03-09, 11:04 PM #23
Edit: Woo I just realized I'm retarded.

The plane will start to move, the conveyor will compensate by speeding up exponentially fast, the tires will instantly blow out from the massive acceleration and speed, and the plane will dive headfirst into the conveyor from the loss of the tires.

Assuming the tires don't ever fail then yeah the plane would eventually lift off.

A good way to think about it is this:

Imagine back when you were a little kid, and you had those matchbox cars. If you ever took those into a grocery store and placed it on the conveyor, you probably had a lot of fun, because the wheels would spin but the car would remain in place. HOWEVER, you could make that car move forward, regardless of the speed of that conveyor. Same concept applies here, except instead of your hand pushing a car forward, you have the turbines of an airplane pushing itself forward.
2007-03-09, 11:16 PM #24
I wasn't sure if we were counting the engines :-(
ᵗʰᵉᵇˢᵍ๒ᵍᵐᵃᶥᶫ∙ᶜᵒᵐ
ᴸᶥᵛᵉ ᴼᵑ ᴬᵈᵃᵐ
2007-03-09, 11:21 PM #25
We have this thread at least once a year, and the verdict is always that the people who answer 'no' are retarded.
2007-03-09, 11:23 PM #26
Originally posted by Cool Matty:
Imagine back when you were a little kid, and you had those matchbox cars. If you ever took those into a grocery store and placed it on the conveyor, you probably had a lot of fun, because the wheels would spin but the car would remain in place. HOWEVER, you could make that car move forward, regardless of the speed of that conveyor. Same concept applies here, except instead of your hand pushing a car forward, you have the turbines of an airplane pushing itself forward.


What I want to know, is what ratio of the force the conveyor belt is pushing with is required to counter it on a wheeled object?
omnia mea mecum porto
2007-03-09, 11:25 PM #27
Originally posted by kyle90:
An airplane is sitting, landing gear down, on the middle of a huge conveyor belt. The belt is programmed such that it travels backwards at the same speed the plane moves forwards. The planes engines are started and throttle up to full power. Does the plane take off?

Yes, it's a Harrier, so the conveyer belt doesn't matter, oh snap. =P

But yeah, the real answer that it does is pretty easy if you understand physics.
2007-03-09, 11:26 PM #28
Originally posted by Roach:
What I want to know, is what ratio of the force the conveyor belt is pushing with is required to counter it on a wheeled object?


It depends on the friction between the landing gear and the axle. In an ideal system there would be no friction at all which means the conveyor belt would be able to spin at infinity speed and the plane would still take off.

Even in real life, the conveyor belt could spin so fast that it would explode and the plane would take off, since the amount of friction is so minute.
2007-03-09, 11:27 PM #29
Jimmy, have you ever been to a Turkish Prison?
error; function{getsig} returns 'null'
2007-03-09, 11:27 PM #30
That makes sense, Jon. Thanks.
omnia mea mecum porto
2007-03-10, 3:44 AM #31
If conveyor is programmed to move backwards with the same speed, as plane moving forward, then it will accelerate, as the plane will move forward - and wheels on plane chassis would be rotating with twice the speed.

(Alternatively, if conveyor rotates with the same speed, as wheels on chassis, then conveyor will be constantly accelerating, and in turn, accelerate wheels, providing a loopback - since plane moves forward also by the jets/propellers, wheels will be always rotating faster then belt, and belt will always be catching up by accelerating. In this case, chances are, that chasssis or belt will jam long before plane will take off. Though, depends on plane. ^_^)

So, if chassis can take the punishment, and conveyor belt is snag-free, plane will take off just fine.
I don`t suffer from the lack of sanity.
It`s others, who have it in excess.
2007-03-10, 3:51 AM #32
Who would build a freaking conveyor belt just for that? Geez.
Star Wars: TODOA | DXN - Deus Ex: Nihilum
2007-03-10, 3:52 AM #33
Probably the Germans.
omnia mea mecum porto
2007-03-10, 5:46 AM #34
Think of it this way - If there was a jet engine on wheels on the same conveyer belt if you powered it up would it eventually roll off the front of the conveyer belt?

Yes it would. The wheels and the ground are irrelevant, the engine is creating thrust by moving the air around it. The wheels can spin backwards with the conveyer belt as fast as they want, the air rushing through the turbine will cause the engine to move fowards relative to the air around it. Since the net movement of the engine is fowards through the air, add wings and you get lift.
The Massassi-Map
There is no spoon.
2007-03-10, 6:43 AM #35
Originally posted by Roach:
Probably the Germans.

Yeah, we did. And guess what my father told me even before we started the experiment:
"Ein Flugzeug fährt nicht, es rollt."
Sorry for the lousy German
2007-03-10, 8:11 AM #36
I thought this was going to be another "snakes on a plane" thread.
"Harriet, sweet Harriet - hard-hearted harbinger of haggis."
2007-03-10, 8:19 AM #37
We went over this in December on my school's CS forum, there are some good explanations there:

https://cs.uwindsor.ca/phpbb/viewtopic.php?t=17267&highlight=airplane+aeroplane

It'll take off, the wheels don't matter.
2007-03-10, 8:25 AM #38
Originally posted by Avenger:
I agree with Roach. The engines create thrust, which moves the plane forward. It's the forward motion that moves air over the wings that creates the lift.


Yeah, but it needs to be moving forward in relation to the air, not the belt. The air around the plane in the only thing that matters, and in this case the plane's wings will have zero velocity WRT the air.

EDIT: Yeah, but if it's just the landing gear on the belt, that wouldn't hold the plane back. The plane will have forward motion no matter what the belt does.
2007-03-10, 8:34 AM #39
Originally posted by Impi:
Yeah, we did. And guess what my father told me even before we started the experiment:
"Ein Flugzeug fährt nicht, es rollt."

Ich weiss, ich weiss.
omnia mea mecum porto
2007-03-10, 9:08 AM #40
Originally posted by Obi_Kwiet:
Yeah, but it needs to be moving forward in relation to the air, not the belt. The air around the plane in the only thing that matters, and in this case the plane's wings will have zero velocity WRT the air.

EDIT: Yeah, but if it's just the landing gear on the belt, that wouldn't hold the plane back. The plane will have forward motion no matter what the belt does.


Unless the tires blow out from the insane acceleration :p
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