A plane on a runway, how smart is r3vlimited?

[erik325i]

Think about it guys - if this were possible, airport designs as we know it would change forever. Airports would only need maybe half the runways they have for landing purposes only. Small planes could take off from the tee box of a par 3 at your local muni. Anyway...

No, you don't get it. The conveyor belt would need to be the same length of a normal runway. Nobody is saying that they would be able to take off in place. The plane would still need to travel forward the same distance and reach the same speed in order to take off. All the conveyor belt is doing is spinning the wheels faster than normal.

-Erik

[erik325i]

You're not following what I'm saying. Put said fan on wheels, then on said treadmill and watch what happens. If the fan is powerful enough, it will propel it self off the front of the treadmill.

agreed

How can you agree that a fan on wheels would propell itself off the front of the treadmill, but not think that an airplane could do it? It's the same exact thing, but on a larger scale.

-Erik

[uofom3]

Why would airspeed never be achieved? The problem with your dyno example is that a car is propelled by the wheels "pushing" against the ground/dyno rollers.

Airplanes are not propelled by engines that directly react with(push against) the ground. They directly react with(push against) the surrounding air/atmosphere. The wheels just go along for the ride.

Imagine for a minute that the plane no longer has wheels and is magically levitating stationary off the ground. Crank up the engines and they will still start to push the plane forward(relative to the ground AND treadmill).

I can imagine poop stains on my underwear that when rubbed against tities make gold - but that doesn't change the fact that, in this case, the wheels are very real, there is no fan pushing on the plane, and the plane is not moving.

I agree that the wheels, unto their own, do absolutely nothing but go along for the ride. The question says that the conveyor belt, which i have been calling a treadmill i guess, matches the potential GROUND speed of the aircraft. Theoretically, X amount of throttle is going to equate to X speed in Mph or other measurement, that allows the aircraft to become airborne. Right? Ok. problem is, the plane HAS TO BE MOVING. The treadmill is stated as MATCHING the aircraft potential speed. The wheels have dick nothing to do with anything, they just happen to be what hits the treadmill.

Scenario:
-Put big ass plane on treadmill/conveyor belt etc.
-Turn on the plane/treadmill
-throttle up plane and match with treadmill
-Plane is now theoretically reaching flight speed, but has NO AIR passing over the wings because IT IS NOT MOVING.
- Plane is now hammering away at full throttle - still sitting on the treadmill that is sitting on the tarmac.

Think about it guys - if this were possible, airport designs as we know it would change forever. Airports would only need maybe half the runways they have for landing purposes only. Small planes could take off from the tee box of a par 3 at your local muni. Anyway...

[DarkWing6]

You're not following what I'm saying. Put said fan on wheels, then on said treadmill and watch what happens. If the fan is powerful enough, it will propel it self off the front of the treadmill.

No it wont because the treadmill in this question will match the speed of the fan.

As the question is read the plane has to move along the treadmill up to a speed where it will take off. This cannot happen because the treadmill is matching the "speed" of the plane in an oposite direction. The wheels are important in this question because they cannot leave the ground until takeoff.

The wheels have to stay connected to the treadmill and the plane has to move forward to take off, so it cannot move forward because the treadmill will not allow it to move forward becasue it is matching the speed of the plane in the opposite direction.

[erik325i]

Ok, how can the wheels go faster than my belt which has a speed of infinity? What speed are the wheels going? infinity + 20mph? Let's just say (for my benefit) that the wheels can not go faster than the belt, does the object still move forward? The answer is No, the object can not move forward unless the wheels are no longer on the belt. That's my take on it.

The Max speed of the belt is infinite. It is not moving at infinite while the plane it taking off, but simply moving at the same speed of the plane.
For example, the plane is traveling 200mph. The conveyor belt is traveling backward 200mph, and the wheels are spinning forward 400mph.

Also, don't tell me that you can't have a speed larger than infinite. Infinite is not an accual number, so you can't directly compare it to other numbers. Please don't make me take out my old Calculous text books to show that you can have a number reach infinite faster than another. I really hated that class and really don't feel like opening that book again, so just get over it.

I don't see how the original question separates the wheel speed from the plane speed. Say for the sake of argument, that I am standing on the conveyor belt with my feet strapped to the belt, and you start this scenario in motion. The plane will be going very fast relative to my position on the belt. I could very easily reference speed of the plane based on my observations standing on the belt. Or in a more realistic situation, say you had a conventional auto speedometer attached to the wheels of the plane and that was how you were measuring speed (speed is a function of wheel diameter and revolutions per unit time). The problem does not say how you are measuring the planes speed, people are jumping to their own conclusions.

Ok, lets say the problem says plane speed is referenced to a fixed point outside of the moving system. The belt will always be moving the same speed that the plane is moving relative to that fixed point. So if the plane speed is 100, the belt would be 100, right? How does the plane ever begin to move? If the belt reaction is instantaneous, and the belt can only go as fast as the plane is moving, the force reactions should cancel eachother out. :-) We are tedering on a paradox here.

It seems that you understand how everything works, except for how the plane speed is measured now...
Once again, you cannot measure the plane speed by the wheel speed.
Imagine you are in your car at a red light. You rev up the engine, drop the clutch, and hold the brake. What's happening now? You are sitting still at the red light, while your back wheels are spinning like crazy. If you look at the speedometer, it is going to say you are going very fast because it judges your speed by the wheel speed. You are traveling 0mph, but the wheels are spinning very fast.
This proves that vehicle speed is different than wheel speed.

You need to judge the speed of the plane against something that is stationary, not something that has a variable speed (like the conveyor belt). Like I said earlier, picture it this way: a state trooper is sitting in his squad car next to the conveyor belt with his radar gun pointed at the plane. The conveyor belt automaticly goes the speed that the radar gun is reading.

Here, read the original question:

This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in opposite direction).

[uofom3]

You're not following what I'm saying. Put said fan on wheels, then on said treadmill and watch what happens. If the fan is powerful enough, it will propel it self off the front of the treadmill.

agreed

[uofom3]

plane would be shot off of the end of the treadmill much like an anorexic bitch collapsing on a treadmill

i lol'ed

[imsotyerred]

the plane will not take off because the treadmill going that fast would create such a great amount of friction on the wheels that the tires would burn off and the plane would be shot off of the end of the treadmill much like an anorexic bitch collapsing on a treadmill

[sticksdaman]

if the conveyor system works as per the question (which states that it instantly matches plane speed) then there will be no movement -no forward movement -no lift -no fly

stationary planes cannot fly if kept stationary

[erik325i]

That basicly means that as long as the wheels are rollers(not driven), the belt will not cancel the movement of plane compared to landscape?

I think that I'm finaly getting this. thanks Erik.

Yes, I'm glad you get it. The belt will not cancel out the effect of the jets.

-Erik

[PiercedE30]

why can't the pulley be pulling the plane forward with the pulley itself being underground (like on an aircraft carrier). then the plane could definitely fly.






i'm too lazy to read 21 damn pages of this shit.

[Jonathan M3]

right, but airspeed will never be achieved relative to the ground, only relative to the treadmill. Because you are not actually moving through the air this is irrelevant. It's like a car on a dyno - you can ramp it up to 160+ but you're strapped to the dyno. Regardless of how fast you stand on it you're not going 150+ relative to the ground - just relative to the dyno. Compared to the ground you're doing 0 on the dyno, and the plane is doing 0 relative to the ground while on the treadmill and generating no lift.

Why would airspeed never be achieved? The problem with your dyno example is that a car is propelled by the wheels "pushing" against the ground/dyno rollers.

Airplanes are not propelled by engines that directly react with(push against) the ground. They directly react with(push against) the surrounding air/atmosphere. The wheels just go along for the ride.

Imagine for a minute that the plane no longer has wheels and is magically levitating stationary off the ground. Crank up the engines and they will still start to push the plane forward(relative to the ground AND treadmill).

[Jonathan M3]

here is even a better example - why do you think that you need to turn on a fan when you run on a treadmill to cool yourself? Think about it, you run on the treadmill and no air is hitting your face other than the stagnant air in the room because YOU ARE NOT MOVING.... just moving relative to the treadmill.

You're not following what I'm saying. Put said fan on wheels, then on said treadmill and watch what happens. If the fan is powerful enough, it will propel it self off the front of the treadmill.

[uofom3]

Of course airspeed has to do with it. Once the engines propel the plane through the air up to the airspeed required for lift, the plane will take off.

right, but airspeed will never be achieved relative to the ground, only relative to the treadmill. Because you are not actually moving through the air this is irrelevant. It's like a car on a dyno - you can ramp it up to 160+ but you're strapped to the dyno. Regardless of how fast you stand on it you're not going 150+ relative to the ground - just relative to the dyno. Compared to the ground you're doing 0 on the dyno, and the plane is doing 0 relative to the ground while on the treadmill and generating no lift.

[uofom3]

here is even a better example - why do you think that you need to turn on a fan when you run on a treadmill to cool yourself? Think about it, you run on the treadmill and no air is hitting your face other than the stagnant air in the room because YOU ARE NOT MOVING.... just moving relative to the treadmill.