A plane on a runway, how smart is r3vlimited?

[chucko]

You guys are making me increase my post count here. I wanted to stay under 100.

[erik325i]

Yes, if the belt is exactly opposite to the speed of the wheels the rocket will go nowhere. Also I am assuming the thrust is horizontal and has no vertical component. If there is a vertical component to the thrust, the planes(or missile) engine could lift the wheels from the belt surface and the plane would move forward relative to the air. Vertical thrust is not a part of this problem though.

Yes, all of the thrust from the missile is horizontal.

Hold on a sec while I laugh my ass off thinking about how you believe the missile will just sit there in space because of the conveyor belt. :rofl:



Is that your final answer? :D

[chucko]

No, you're still not seeing it. The engines are pushing the plane through the air. The conveyor belt has nothing to do with it. Imagine the plane is a missile with some casters attached to it, so it can roll. You launch the missile on the conveyor belt. Are you trying to say that the conveyor belt will keep the missile from going anywhere?

-Erik

Yes, if the belt is exactly opposite to the speed of the wheels the rocket will go nowhere. Also I am assuming the thrust is horizontal and has no vertical component. If there is a vertical component to the thrust, the planes(or missile) engine could lift the wheels from the belt surface and the plane would move forward relative to the air. Vertical thrust is not a part of this problem though.

[tonytony]

OMFG this is rediculous, the damn wheels do not provide thrust. I'm no engineer, art major actually, but seriosly this is being made harder than it actually is. I interpreted as the conveyer belt being as a run way that moves in the opposite direction of the plane. so, say a person on a treadmill running theyr'e goin nowhere until an outside force(someone kicking them from behind) propels them foward. the original question never said that there was no air, if air is out of the situation it would be in a vaccum. It would be a space craft, even then it would still be thrusted foward by it's fuel. It wont fly because there is no air to give it lift. The wheels have no effect on the foward movement of the plane, otherwise it would fall out of the sky if the wheels provide any sort of thrust.

[erik325i]

Yes and No, the air is actually outside of the system (system being the wheels of the plane and the conveyor belt) and as far as the air is concerned, the plane is not moving at all with respect to how the air is moving. You all are neglecting the fact that the jet engine is attached to the plane which is attached to the wheels which are touching the conveyor belt. So the conveyor belt counter-speed has to be over come in order for the plane to move relative to the air. Since the belt is exactly matching the speed of the wheels of the plane, it can not over come the belt counter-speed.

No, you're still not seeing it. The engines are pushing the plane through the air. The conveyor belt has nothing to do with it. Imagine the plane is a missile with some casters attached to it, so it can roll. You launch the missile on the conveyor belt. Are you trying to say that the conveyor belt will keep the missile from going anywhere?

-Erik

[chucko]

Fine, it doesn't really matter how you measure the speed to calculate the speed of the conveyor belt.

What does matter is how fast the plane is traveling in relation to the air. The jet engines push the plane forward though the air. The engines will continue to push the plane though the air untill it has reached a speed fast enough to take off. The speed of the conveyor belt has no effect.

-Erik

Yes and No, the air is actually outside of the system (system being the wheels of the plane and the conveyor belt) and as far as the air is concerned, the plane is not moving at all with respect to how the air is moving. You all are neglecting the fact that the jet engine is attached to the plane which is attached to the wheels which are touching the conveyor belt. So the conveyor belt counter-speed has to be over come in order for the plane to move relative to the air. Since the belt is exactly matching the speed of the wheels of the plane, it can not over come the belt counter-speed.

[erik325i]

No you are wrong. You, like Justin, are trying to reference speed from outside of the system and applying that to the system. That's like standing on the moon and measuring the speed of a car on the earth while the earth is spinning 1700 km/hr and saying that the car is moving at 1720km/hr when on the earth the car is only moving at 20km/hr. The conveyor belt can not measure the speed of the plane from outside of the system, it measures the speed of the plane from within the system.

Fine, it doesn't really matter how you measure the speed to calculate the speed of the conveyor belt.

What does matter is how fast the plane is traveling in relation to the air. The jet engines push the plane forward though the air. The engines will continue to push the plane though the air untill it has reached a speed fast enough to take off. The speed of the conveyor belt has no effect.

-Erik

[chucko]

Chucko, you are completely wrong.

Put a toy plane on a treadmill, and hold it in place with your hand. You will now see that the top plane is traveling 0mph, while the wheels are indeed spinning faster than the plane.

Please read the example I quoted above by Brew, and get back to me.

-Erik

No you are wrong. You, like Justin, are trying to reference speed from outside of the system and applying that to the system. That's like standing on the moon and measuring the speed of a car on the earth while the earth is spinning 1700 km/hr and saying that the car is moving at 1720km/hr when on the earth the car is only moving at 20km/hr. The conveyor belt can not measure the speed of the plane from outside of the system, it measures the speed of the plane from within the system.

[erik325i]

Let me say this, my conveyor belt is assuming wheel speed = plane speed, no reason to believe otherwise.

Chucko, you are completely wrong.

Put a toy plane on a treadmill, and hold it in place with your hand. You will now see that the toy plane is traveling 0mph, while the wheels are indeed spinning faster than the plane.

Please read the example I quoted above by Brew, and get back to me.

-Erik

[erik325i]

Holy Shit, you guys still don't get it.

The wheels are only there to hold up the plane. The thrust is provided by jet engines.

I want everyone to read Brew's example before blabbing on about the plane not moving.

I can't believe people are still arguing this.

Forget the plane, picture a missile sitting on the same runway with a few casters on it. Someone try and tell me that it wont accelerate, I dare you.

[chucko]

I understand this whole situation is fake. I understand everything you're talking about. I am chill, all I want to know is how your conveyor belt prevents my plane from creating thrust and moving forward. Let me know that and I'll stop posting. Of course that wont happen though :)

Let me say this, my conveyor belt is assuming wheel speed = plane speed, no reason to believe otherwise. My conveyor belt has a max speed of inifinity. In order to take off, you will have to be traveling at infinity+100mph (or so, right?), not possible by the definition of infinity. This is not a leap, I've made two assumptions which are not outside of what the problem allows.

The only way a belt can hold an airplane back anyway is if the wheels had really bad rolling resistance and the belt spun fast enough to cancel out any thrust from the engine. Simple as that, but that isnt happening, the plane moves, and is allowed to accelerate.

How do you know that isn't happening? The problem does allow for that possibility. In fact I'd say the problem suggests that.

Regarding the wheel speed vs belt speed, you're failing to recognize something very important. The speed of the aircraft is A, okay? The speed of the belt is B (well thats handy huh), okay?

There's your flaw right there. How does A not equal B? If the plane is at rest when the scenario begins (problem says this), how does the plane's wheels ever move faster than the plane? How are you determining speed? In this case you can't reference speed to a fixed point outside of the system, cause the system is moving, you have to reference speed within the system. So speed is related to wheel revolution or distance from fixed point on the conveyor belt per unit time (has to be within the system). Think about how your cars speedometer measures speed. The same would be true here.

You can agree to disagree, but I cant let false answers rule.

OK, I will agree to disagree and my false answers will rule. :-)

[O 16581 72452 5]

Let's take out the variable of the conveyor breaking, the wheels falling off, etc, it's thrust that moves the plane, even after it gets some speed and this stuff breaks, it's still moved by thrust and will drag it's ass on the underbody until it can lift.

If looked at from the view as the plane speed being wheel RPM related (like you'd see on a speedometer in some type of instrument cluster), i can't really say what would happen, it'd move infinately fast until something broke, the plane wouldn't even have to be on for this to happen though, the conveyor could just kick on and move the wheels at the exact same speed as the system and it'd infinately not go anywhere (in a friction free world).

But from the information provided, the plane must have an actual speed, which would mean it'd move in relation to air and be going an actual distance.

[Justin B]

I think a full post just announcing myself going to bed is perfectly OK. I think so. Yeah. I'm going to bed.

Damnit, I cant just leave it at that. Think about it a little for me, and please don't reply a whole lot with more fun stuff to explain why its wrong about how a plane is supposed to be a car. I do see where you're coming from now, and have for a few posts, but you're putting all the drive in the wheels, not in the prop or jet engine literally dragging the plane on whatever surface it travels on. Thats why they have wheels though, just to keep them from dragging on their fuselage, that could be a serious problem, and it wouldnt work quite well :P

[Justin B]

There is nothing in the problem which states this is the case. You're suggesting the plane can move for a fraction of a second before the belt moves right? If you design some fictitious control system which reacts to the thing that's touching it (the wheels) and its reaction is intstantaneous, the wheels will NEVER spin faster than the belt, no matter how much thrust you apply. If the wheels never move faster than the belt, the plane does not take off. That's my angle.

I need a separate reply to piece out a portion of your reply.

IT IS NOT A CAR. The drive does not come from the wheels. Of course you could put a car on a conveyor belt and set something up like that so the car is always stationary, and the belt is spinning as fast as the wheels are but the wheels provide no forward "push" to the plane, if they did, then sure, you could prevent the plane from moving at all. The problem there with your logic is that the plane has these things called engines with props or jets, and they pull air from one side to the other :) That pulls the aircraft forward, creating wheel speed, lets just say the plane moves 10 feet, and the conveyor belt moves back 10 feet to "negate" that 10 feet that the wheels just moved. Too bad the wheels didn't drive, they got pulled, there is a difference there. The wheels are already 10 feet to the right of the center point of where everything started, while the point that which was under the wheels is now 10 feet behind the center point. A 20 foot difference, all in the same time that each individual major piece (plane and belt) moves 10 feet hte wheels moved 20, hence twice the speed. Its easy math man, the plane pulls the wheels along, they follow it, the wheels dont drive the plane, in which case a very smart fictitious belt with 0 reaction time COULD keep in one exact position, I do not argue that fact at all. I just try to point out that that is not how planes work.

[O 16581 72452 5]

Like i said to Justin on AIM, this whole situation is pretty obsolete, it's discussing airplane speed which if taken literally, would be it's speed in a measureable distance (miles per hour), the plane has to be moving in relation to a distance, it has to be going somewhere to have speed. If the conveyor is moving 200mph backwards, the plane has to still be moving forward at 200mph for the conveyor to be moving backwards at 200mph. Even if the plane were powered by the wheels like a car, this would still have to be the case, unless you read the speed through the speedometer, which wouldn't be right, the wheels would be traveling a speed (not really, it'd just be making RPMs, but the speedometer would give a reading). But the actual car would be going 0 miles per hour, therefor has no speed and the conveyor wouldn't move either.

Get it..?