A plane on a runway, how smart is r3vlimited?

[Fidhle007]

*hug*

If you need to talk we're here buddy! :)

[sticksdaman]

ok consider this...

in order for the plane to move forward it has to gain ground which is theoretically impossible due to the scenario of the question -the conveyor cancels out any forward movement attempted by the wheels (or the plane). the wheels wont move forward and if the wheels cant move forward the plane can not move forward since they are connected. and the plane WONT move forward WONT generate lift WONT take off

[ptownTSI]

ok consider this...

in order for the plane to move forward it has to gain ground which is theoretically impossible due to the scenario of the question -the conveyor cancels out any forward movement attempted by the wheels (or the plane). the wheels wont move forward and if the wheels cant move forward the plane can not move forward since they are connected. and the plane WONT move forward WONT generate lift WONT take off

The plane moves forward while the wheels rotate backwards. The plane is still traveling forward gaining speed, flowing air over the wings, resulting in lift.

the plane wheels are not connected towards providing thrust for the plane, they will simply spin beneath it regardless of what the belt does. PLEASE READ MY SKATEBOARD example on the previous page, it will explain this to you.

[gstuning]

The final post.

Rules of the world.
Bearings create friction.

Part 1.
airplane is tied to a rope wich is tied to a weight or strain gauge wich is then tied to the solid ground, it´s also sitting on a conveyor belt,.
By setting the belt in action two things happen.
The plane WILL sit still as it´s tied to the ground,
The strain gauge will show added force from the plane as the friction of the wheels is trying to pull the plane backwards, as the tires are rolling backwards because the belt is rolling backwards.
This we all know and agree on,

What we know now is that the conveyor belt exerts backwards motion to the plane by the bearing friction,

Part 2.
Everything is the same, now if you where to put the conveyor belt to the airplanes double take off speed only backwards as before,
Now the wheels should be putting more backwards motion to the plane but it´s still tied to the ground, so it´s not going anywhere.

Part 3

Now we need to know if the planes engines have enough thrust to overcome the backwards motion and relieve the strain from the rope and gauge,
i.e to overcome the backwards motion of the belt, wich is turning at the planes double take off speed. (double take off speed is the same wheel speed if the belt is always moving at the same speed backwards as the plane is moving forward when it´s trying to take off)

Part 4 and Conclusion
If the planes thrust can overcome the belts speed backwards.
The plane as has overcome the friction and is thus capable of flying .

There is no dissputing this as all the variables have been covered.

The only reason the airplane will not fly is if it can not overcome the friction of the wheel bearings going backwards at twice the take off speed as is required of the original question.

Now I´m going to assume that ALL planes have this cabability as they all easily enough over come the bearings at the take off speed anyway.
And thus the final is that indeed the plane will fly.

Now there are no othere variables in this but the bearings friction as the weight of the airplane is the same as on normal ground. and the take off speed does not change, nothing is diffrent exept the speed of the wheels.

Now you can take that to the bank and cash it

Don´t post anymore just re read it until you DO understand

[DarkWing6]

I talked to some guys at work and I understand it now...

[RobertK]

you are fucking stupid.

put a skateboard on a treadmill, put the speed to 2 mph, can you hold the skateboard in a stationary position with the wheels rolling backward?

yes.

put the speed to 5mph

can you still hold it?

yes

What I have just demonstrated is equivalent to the jet engine overcoming the friction of the wheels, you hand is acting like the jet engine.

Now push the skateboard forward, does the skateboard not move forward even with the wheels spinning backwards?

yes it does.

your hand is no different than a jet engine.

you could put the treadmill to 1000mph and your hand would still be able to push it forward, just like the jet engine. It could still easily get up to speed and take off.

Your anaolgy is very wrong.. Using your hand against the skateboard you will have to brace the skateboard down with more downward and forward force to keep it at 0mph. Crank a treadmill up to 1000mph and lets see how long you can hold that fucker in place using the same downward and bracing force you did at 5mph.

[deansbimmer]

The jet will still take off. Aircraft obviously dont rely on groundspeed, only airspeed. The wheels could be rotating and still accelerating at the speed of sound on the conveyor, but as long as the turbine has the thrust to overcome that drag, (which it does) the plane will move forward and take off.

[DarkWing6]

Lets just say the speed at takeoff is 150mph (I don't really know and it doesn't matter)

The 150mph the the plane is traveling is air speed. The 150mph the the treadmill, conveyor belt, whatever is traveling is 150mph ground speed. With this said the wheels would be spinning at 300mph, with the plane moving forward because the belt only changes the speed of the wheels and not the air speed of the plane.

[E30 Wagen]

Your anaolgy is very wrong.. Using your hand against the skateboard you will have to brace the skateboard down with more downward and forward force to keep it at 0mph. Crank a treadmill up to 1000mph and lets see how long you can hold that fucker in place using the same downward and bracing force you did at 5mph.

You put your hand behind the skateboard to hold it in place... He never said anyting about pressing down on top of it.

.
.
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And to reiterate gstuning's post: Think about the forces a plane must overcome in order to take off on stationary groud. The only thing that's changed is an increased resistance of the faster spinning wheels.

Let's take a plane and put some blocks in front its wheels so that it can't move. Now, set the propeller spinning at a constant RPM, but not fast enough to make the plane take off. Remove the blocks and what happens? The propeller pulls the plane forward, of course. Let's say that the maximum speed the plane can achieve is a constant 30mph. It has reached the maximum amount of friction created by the wheel bearings of which the thrust of the propeller could not overcome, effectively "stopping" it at 30mph.

Do the same thing but on our dreaded moving runway. We put blocks in front of the wheels to keep the plane from moving, and we set the propeller spinning at exactly the same RPM as we did on stationary ground. What happens when we remove the blocks? The plane will go forward. As the plane goes forward, the belt matches the rate of acceleration. The plane thinks that eventually it's going to hit a top speed of 30mph. However, because the wheels are spinning faster, generating more heat and more friction, the plane will be "stopped" at a slower top speed, let's say 29mph. In order for the plane to hit 30mph, we simply increase the propeller's RPM.

And again, I am sure that the increased friction of the spinning wheels is next to nothing and that we could throttle the propeller up to a higher RPM and the plane will be able to get up to speed enough to take off.

[RobertK]

You put your hand behind the skateboard to hold it in place... He never said anyting about pressing down on top of it.

What I'm getting at is that the skateboard analogy is flawed because you are not accounting for the amount of force being place on the skateboard. Holding a 10lb object in place with you arm is like putting 10 jet engines on an cessna. Of course it would take very little work to keep the damn thing in place.

Place a scale between the hand and the back of the skateboard and there will be an amount of mearsured force there.

If you read some of my posts you would understand that there is alot more to just saying.. "Oh the jet flys with air speed and the wheels are not relative." which is completely wrong.

What I had discussed is that in the real world the weight of the plane, the amount of possible thrust, and wheels size is important because it plays a significant roll in the amount of friction & drag created at the wheels and the conveyor.

Furthermore I would like to add the number of wheels on the plane is also important because the more wheels a plane has the more surface area there is to produce friction and drag between the converyor and the plane.

Remember the question is not HOW a plane is able to fly the questions is will it take off.

The conclusion is that if the plane is properly built and balanced with enough thrust to overcome the backward thrust of the conveyor. Since there is no such wheel that is 100% efficient at the transfer of energy the wheels can neither produce 100% negative drag nor 0% drag. Thus eventually enough thrusting force would push it down the conveyor.

My second conclusion is that there is a high probability no planes in current existance could overcome this feat but it is highly possble to build one that could.

[benDASHDASH]

REFUSE TO BELIEVE

[DarkWing6]

lol

[Fidhle007]

I seriously can't believe we're on Page 25 already, the only discrepancy between whether or not the plane will lift off is due to how you are calculating the speed. If the original question had said that the conveyor belt would move at exactly the same speed as the planes INDICATED GROUND SPEED then no, the plane would never take off. It would remain stationary and neve move. However, if (because it's an airplane, and ground speed is there for moot) you say the conveyor will move at the same speed as the planes ACTUAL FORWARD SPEED, airspeed for example, then yes, the plane will be moving forward and given the right conditions will generate enough lift to take off. Friction will be a small factor but the point is the plane would be moving forward. I don't want to hear another goddamn thing from any of you until you can agree HOW YOU ARE MEASURING THE PLANE'S SPEED.

Have fun...

[benDASHDASH]

I seriously can't believe we're on Page 25 already, the only discrepancy between whether or not the plane will lift off is due to how you are calculating the speed. If the original question had said that the conveyor belt would move at exactly the same speed as the planes INDICATED GROUND SPEED then no, the plane would never take off. It would remain stationary and neve move. However, if (because it's an airplane, and ground speed is there for moot) you say the conveyor will move at the same speed as the planes ACTUAL FORWARD SPEED, airspeed for example, then yes, the plane will be moving forward and given the right conditions will generate enough lift to take off. Friction will be a small factor but the point is the plane would be moving forward. I don't want to hear another goddamn thing from any of you until you can agree HOW YOU ARE MEASURING THE PLANE'S SPEED.

Have fun...

[DarkWing6]

This is more like it for Ben. :D



EDIT - If I had Pshop at work I would have made the sign say "Magic BTM" (BTM is Ben's initials).