That plane, and it taking off.

[FusionKnight]

Originally posted by: JujuFish

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong 🙂

FK

Right there.

So if the plane is moving at a speed of 10mph forward relative to the conveyor belt which is moving at a speed of 10mph opposite to the motion of the plane, the plane would appear to move forward along the conveyor to a bystander? If this is the case, why?

FK

 

[JujuFish]

Originally posted by: FusionKnight
So if the plane is moving at a speed of 10mph forward relative to the conveyor belt which is moving at a speed of 10mph opposite to the motion of the plane, the plane would appear to move forward along the conveyor to a bystander? If this is the case, why?

FK

Because the only instance where that can occur is when the reference point is air. The plane will be moving forward, the conveyor belt backward, and the wheels will be moving at twice their normal speed.

 

[FusionKnight]

Originally posted by: JujuFish

Originally posted by: FusionKnight
So if the plane is moving at a speed of 10mph forward relative to the conveyor belt which is moving at a speed of 10mph opposite to the motion of the plane, the plane would appear to move forward along the conveyor to a bystander? If this is the case, why?

FK

Because the only instance where that can occur is when the reference point is air. The plane will be moving forward, the conveyor belt backward, and the wheels will be moving at twice their normal speed.

Ok, so is what I said true or false? Because if it's true, then I still don't understand why it would take off, and if it's false I don't understand why it's false.

FK

 

[Squisher]

Originally posted by: JujuFish

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong 🙂

FK

Right there.

Who said there is no forward movement? All that was said was that the conveyor would move at the same speed as the wheels. The wheels don't make it move, the prop does.

From the other thread:

Let's pretend the plane is flying at 200mph. I hang out of the plane and attach a treadmill under its wheels and cause the wheels to spin at 200mph.

WILL THE PLANE FALL OUT OF THE SKY??????????

 

[JujuFish]

Originally posted by: FusionKnight

Originally posted by: JujuFish
Because the only instance where that can occur is when the reference point is air. The plane will be moving forward, the conveyor belt backward, and the wheels will be moving at twice their normal speed.

Ok, so is what I said true or false? Because if it's true, then I still don't understand why it would take off, and if it's false I don't understand why it's false.

FK

It's false, and it takes off because it moves forward, gains the appropriate velocity. The wheels are free to roll. A plane does not use the wheels to push itself forward like a car does.

 

[FusionKnight]

OMG I totally just got it. For some reason, I figured the wheels would provide some crazy resistance against the plane's movement, which is obviously not the case. The wheels would just free spin due to the movement of the conveyor, and the engines would propel the plane forward regardless. *slaps forehead*

FK

Edit: Yeah I realized the wheels had nothing to do with propelling the plane forward, but for some reason I thought there would be some significant resistance on the wheels.

 

[KingofCamelot]

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong 🙂

FK

Wheels have nothing to do with a plane moving forward. The only purpose the wheels moving on take off serves is to not have something metal grinding against the ground. I'm going to try to put this a different way you might understand (though my logic may be flawed):

You are running on a totally lubricated, frictionless treadmill. The treadmill is not powered, but the belt will move with the slightest touch. So, if you try to start running on the treadmill, you won't be going anywhere relative to the ground because you push against the the belt, and the belt moves, so everytime you push against the belt, it moves backwards. No matter how fast you run this happens, so you remain stationary to the ground.

Now, someone pushes you from behind. What happens? You fall on your face. Why? Because the force was not applied to the treadmill, it was applied to your body. When you run your feet push against the belt. When someone pushes you, the force is against your body, and your feet do not apply any more force against the belt. If the person continued pushing you with gradual force, not enough that you are knocked over, you will start moving forward.

Apply that to the airplane. The force of the airplane's engines does not effect the wheels, they simply speed up because they are pushing against the ground. If the ground gives everytime they push, does that mean that airplane isn't being forward by its engines? Of course it is.

A different way to put it:

Hang a toy airplane from the ceiling, and start its engines. It starts moving forward because it is pushing against the air. Now add motorized wheels to it moving at 5 MPH. The wheels in effect remain in the same place, because they push against the air, but it the friction isn't enough to move it. Even though the wheels aren't moving relative to the ground, the airplane moves. So, even though the wheels on the treadmill aren't moving relative to the ground, the airplane still moves.

EDIT: Heh, thats what I get for grabbing a drink midway through typing a reply...question already answered 10 minutes earlier.

 

[smack Down]

The question just sucks as worded.

 

[Kenazo]

Originally posted by: JujuFish

Originally posted by: FusionKnight
So if the plane is moving at a speed of 10mph forward relative to the conveyor belt which is moving at a speed of 10mph opposite to the motion of the plane, the plane would appear to move forward along the conveyor to a bystander? If this is the case, why?

FK

Because the only instance where that can occur is when the reference point is air. The plane will be moving forward, the conveyor belt backward, and the wheels will be moving at twice their normal speed.

You're missing part of the question. The original post said that the conveyer will be going the same speed as the wheels, thus it's an impossibility, as worded. The conveyer will just keep going faster and faster and nothing will happen.

 

[JujuFish]

Originally posted by: Kenazo
You're missing part of the question. The original post said that the conveyer will be going the same speed as the wheels, thus it's an impossibility, as worded. The conveyer will just keep going faster and faster and nothing will happen.

On the contrary, you're misinterpretting it. Show me, in either of the following two OPs where that is a stipulation:

Originally posted by: 911paramedic
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. 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 the opposite direction). Can the plane take off?"

Originally posted by: NanoStuff
The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.

 

[cKGunslinger]

Originally posted by: deathkoba

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong 🙂

FK

Yes you're correct. I don't understand why these so called physics geniuses can't figure out such a simple thing. It's like OMG, a plane's wheels will move without any power applied! It will if it were on a hill.

*shakes head*

I hope your "dinner dates" are all blonde, else the night's conversations will all be completely over your head. :laugh:

 

[JujuFish]

Originally posted by: cKGunslinger

Originally posted by: deathkoba

Originally posted by: FusionKnight
Ok I seriously still don't get it. If the plane is *always* moving at the same speed as the conveyor, I wouldn't think it would take off because with respect to the ground and the air surrounding the plane, there is no forward movement. This forward movement, I thought, was what caused the air to flow across the wings and generate the lift required to get the plane off the ground. Someone tell me where in the above that I'm wrong 🙂

FK

Yes you're correct. I don't understand why these so called physics geniuses can't figure out such a simple thing. It's like OMG, a plane's wheels will move without any power applied! It will if it were on a hill.

*shakes head*

I hope your "dinner dates" are all blonde, else the night's conversations will all be completely over your head. :laugh:

Ouch. 😛

 

[NanoStuff]

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: FusionKnight
So if the plane is moving at a speed of 10mph forward relative to the conveyor belt which is moving at a speed of 10mph opposite to the motion of the plane, the plane would appear to move forward along the conveyor to a bystander? If this is the case, why?

FK

Because the only instance where that can occur is when the reference point is air. The plane will be moving forward, the conveyor belt backward, and the wheels will be moving at twice their normal speed.

You're missing part of the question. The original post said that the conveyer will be going the same speed as the wheels, thus it's an impossibility, as worded. The conveyer will just keep going faster and faster and nothing will happen.

Again, the cogs. It's very possible. The conveyor will only 'go' as fast as the wheels.

 

[JujuFish]

Originally posted by: NanoStuff
Again, the cogs. It's very possible. The conveyor will only 'go' as fast as the wheels.

Says the one who hasn't taken physics.

 

[Kenazo]

Originally posted by: JujuFish

Originally posted by: Kenazo
You're missing part of the question. The original post said that the conveyer will be going the same speed as the wheels, thus it's an impossibility, as worded. The conveyer will just keep going faster and faster and nothing will happen.

On the contrary, you're misinterpretting it. Show me, in either of the following two OPs where that is a stipulation:

Originally posted by: 911paramedic
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. 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 the opposite direction). Can the plane take off?"

Originally posted by: NanoStuff
The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.

The stipulation above is kind of like dividing by zero.

 

[JujuFish]

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo
You're missing part of the question. The original post said that the conveyer will be going the same speed as the wheels, thus it's an impossibility, as worded. The conveyer will just keep going faster and faster and nothing will happen.

On the contrary, you're misinterpretting it. Show me, in either of the following two OPs where that is a stipulation:

Originally posted by: 911paramedic
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. 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 the opposite direction). Can the plane take off?"

Originally posted by: NanoStuff
The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

 

[Kenazo]

Originally posted by: JujuFish

Originally posted by: Kenazo

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

It is impossible for something to roll forward if a conveyer is moving in the opposite direction at the same speed, and accelerating at the same speed. It has nothing to do with if the wheels are driven or not. Basically nothing will happen given the stipulation I highlighted before. It's not a physics problem, it's just a stupidly worded question.

 

[JujuFish]

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

It is impossible for something to roll forward if a conveyer is moving in the opposite direction at the same speed, and accelerating at the same speed. It has nothing to do with if the wheels are driven or not. Basically nothing will happen given the stipulation I highlighted before. It's not a physics problem, it's just a stupidly worded question.

It is not impossible. The wheels are free to rotate. Planes don't work like cars; they don't need to "push" off of the ground with their wheels to move forward. The wheels would just move twice as fast.

 

[Kenazo]

Originally posted by: JujuFish

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

It is impossible for something to roll forward if a conveyer is moving in the opposite direction at the same speed, and accelerating at the same speed. It has nothing to do with if the wheels are driven or not. Basically nothing will happen given the stipulation I highlighted before. It's not a physics problem, it's just a stupidly worded question.

It is not impossible. The wheels are free to rotate. Planes don't work like cars; they don't need to "push" off of the ground with their wheels to move forward. The wheels would just move twice as fast.

And then the conveyer would move twice as fast and no motion would result. It's just a logic problem, and has nothing to do with actual movement.

 

[JujuFish]

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

It is impossible for something to roll forward if a conveyer is moving in the opposite direction at the same speed, and accelerating at the same speed. It has nothing to do with if the wheels are driven or not. Basically nothing will happen given the stipulation I highlighted before. It's not a physics problem, it's just a stupidly worded question.

It is not impossible. The wheels are free to rotate. Planes don't work like cars; they don't need to "push" off of the ground with their wheels to move forward. The wheels would just move twice as fast.

And then the conveyer would move twice as fast and no motion would result. It's just a logic problem, and has nothing to do with actual movement.

No, the conveyor would not move twice as fast. What you bolded specifically states that the conveyor matches the plane speed, not the wheel speed. You may try arguing semantics on the latter OP, but your argument most certainly does not hold water on the former.

 

[Kenazo]

Originally posted by: JujuFish

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

Originally posted by: JujuFish

Originally posted by: Kenazo

The stipulation above is kind of like dividing by zero.

How so? The plane moves in one direction, the conveyor in another. It will slightly affect the plane, but not significantly.

It is impossible for something to roll forward if a conveyer is moving in the opposite direction at the same speed, and accelerating at the same speed. It has nothing to do with if the wheels are driven or not. Basically nothing will happen given the stipulation I highlighted before. It's not a physics problem, it's just a stupidly worded question.

It is not impossible. The wheels are free to rotate. Planes don't work like cars; they don't need to "push" off of the ground with their wheels to move forward. The wheels would just move twice as fast.

And then the conveyer would move twice as fast and no motion would result. It's just a logic problem, and has nothing to do with actual movement.

No, the conveyor would not move twice as fast. What you bolded specifically states that the conveyor matches the plane speed, not the wheel speed. You may try arguing semantics on the latter OP, but your argument most certainly does not hold water on the former.

🙂 Yeah, I thought I'd bolded both parts.... OK I didn't I bolded the wrong part. My mistake.

Whatever the case, using the second stipulation, there is for sure no way that this could happen. If the belt is just moving the same speed as the wheels, but in the opposite direction the plane could not be moving forward, unless the plane was skidding across the conveyer.

 

[blahblah99]

Originally posted by: letdown427
You all know the question, conveyor belt etc etc, if not just search for it.

Let's see how AT is split on this. It'll be fun.

And as \/ \/ said, obviously it won't settle it, physics > democracy 🙂

Sorry, democracy, like religion, is something that humankind have made up. The laws of physics have been proven over and over and over and over again.

 

[blahblah99]

Originally posted by: 91TTZ

Originally posted by: deathkoba


The plane will take off only if it's engine can generate enough thrust to push the plane even harder than it already is doing, (which is what's keeping it visually stationary in the first place) to the point where there is enough airspeed for take off. So the real answer is YES or NO depending on the performance of the engine and how fast that conveyor belt is moving and whether or not the conveyor belt is adjusting it's speed in realtime as the plane's engine makes adjustments. That plus other environmental factors that affect flight performance directly or indirectly. It's common sense folks.

For the most part, it doesn't matter what the belt is doing, since the plane is just rolling.

My previous example was taken to the extreme, and isn't realistic.

If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

Bingo! Why is that so hard to comprehend for some people?

 

[NanoStuff]

Originally posted by: blahblah99

Originally posted by: 91TTZ

Originally posted by: deathkoba


The plane will take off only if it's engine can generate enough thrust to push the plane even harder than it already is doing, (which is what's keeping it visually stationary in the first place) to the point where there is enough airspeed for take off. So the real answer is YES or NO depending on the performance of the engine and how fast that conveyor belt is moving and whether or not the conveyor belt is adjusting it's speed in realtime as the plane's engine makes adjustments. That plus other environmental factors that affect flight performance directly or indirectly. It's common sense folks.

For the most part, it doesn't matter what the belt is doing, since the plane is just rolling.

My previous example was taken to the extreme, and isn't realistic.

If a jet's takeoff speed is 200 mph, and the belt is moving backwards at 200 mph, the plane will still take off just as easily. The only difference will be that the wheels will be turning at 400 mph.

Bingo! Why is that so hard to comprehend for some people?

Because some people are aware of the 200mph clocked on the belt while other choose to ignore it's impact on the plane. The plane would take off, but only if it exerts twice the thrust it otherwise would have.

 

[jagec]

Originally posted by: Kenazo

Whatever the case, using the second stipulation, there is for sure no way that this could happen. If the belt is just moving the same speed as the wheels, but in the opposite direction the plane could not be moving forward, unless the plane was skidding across the conveyer.

Angular velocity. Linear velocity. They're not the same thing. "Forward" is linear velocity" "Turning", or "around", is angular velocity.

Originally posted by: NanoStuff
The plane increases it's thrust and the wheels begin to rotate. The belt compensates for the rotation of the wheels in reverse, as in the belt moves in reverse exactly as fast as the wheels move forward.

Y HLO THAR, it's our friend Mr. LINEAR velocity!!!

The only part of that phrase that's unclear is the "belt compensates for the rotation...", but that is clarified by the second half of the sentence, which eliminates the angular velocity interpretation.