You have a plane and a conveyor belt.

[PurdueRy]

post #1000!

People need to stop thinking the conveyor imparts a large force on the body of the aircraft...but I have a feeling that would solve nothing

 

[BrokenVisage]

Originally posted by: PurdueRy
post #1000!

Damn you!

 

[Armitage]

Originally posted by: hellokeith
It does need to be said that framing this fantasy situation in another way, such as the stationary winch or rope-tied-to-wall, is faulty due to different forces being involved.

The free body diagram of a plane with its engines providing the thrust is identical to the FBD of a plane being pulled down the treadmill by a winch. The forces are identical. But don't believe me - draw the FBD yourself.

Many have said that a plane is not a car. This is quite true. A plane is also 1) not a person on a treadmill pulling a rope and 2) not being winched anywhere.. unless it steered off the fictitious conveyor and crashed.

 

[PurdueRy]

Originally posted by: BrokenVisage

Originally posted by: PurdueRy
post #1000!

Damn you!

you can hald post #2000

You know its gonna happen....

 

[Rogodin2]

It does need to be said that framing this fantasy situation in another way, such as the stationary winch or rope-tied-to-wall, is faulty due to different forces being involved. Many have said that a plane is not a car. This is quite true. A plane is also 1) not a person on a treadmill pulling a rope and 2) not being winched anywhere.. unless it steered off the fictitious conveyor and crashed.

I think the RC plane pulling a person on a treadmill (moving in reverse) - that can read the speed of the wheels and moves in the opposite direction based on wheel speed - is a fairly close analogy

Rogo

 

[DrPizza]

Originally posted by: mugs

Originally posted by: CVSiN
Dude.. how the hell do you figure..
a treadmill with an F/A-18 sitting on it and thrusting up and its not tied down will try to move forward.. but instead of moving forward the treadmill will move.. so the aircraft will sit idle just like its tied down. no amount of thrust is going to move it off the treadmill.
so how do you get the 150kts of wind under the wings to initiate take off?

Here's another simple analogy - suppose you have a FWD car with the rear wheels on the treadmill and the front wheels off the treadmill. Can the car move? Of course. Because the treadmill does not counteract its source of propulsion. Now apply that to the plane - ALL of the wheels freely rotate and the source of propulsion is the turbines which are not in any way affected by the treadmill.

Great analogy.

 

[HeroOfPellinor]

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

 

[PurdueRy]

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

I am picturing a aircraft with just a rocket attached. However, I am interested how the wheels provide a force to the ground that equals the forward force the engines generate...Can you explain that? Because that is what you are implying

 

[Armitage]

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

A helicopter works the same way a propeller does - it's all bernoulli - no friction involved. What the hell does running in zero gee have to do with it? Or a feather?

I'm really curious about your previous theory - about friction with the ground being required to increase airspeed. Fascinating - please elaborate.

 

[HeroOfPellinor]

Originally posted by: Armitage

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

A helicopter works the same way a propeller does - it's all bernoulli - no friction involved. What the hell does running in zero gee have to do with it? Or a feather?

I'm really curious about your previous theory - about friction with the ground being required to increase airspeed. Fascinating - please elaborate.

Does the space shuttle use a jet turbine engine?

 

[Don Vito Corleone]

Originally posted by: HeroOfPellinor

Does the space shuttle use a jet turbine engine?

No, it uses rockets.

For purposes of this question, it's irrelevant whether the plane is powered by jets, props, or rockets. What matters is that it ISN'T driven by its wheels. This is the same reason a turbine-powered Bonneville Salt Flats car wouldn't be stopped by a really fast conveyor belt, but a top fuel dragster would.

 

[Armitage]

Originally posted by: HeroOfPellinor

Originally posted by: Armitage

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

A helicopter works the same way a propeller does - it's all bernoulli - no friction involved. What the hell does running in zero gee have to do with it? Or a feather?

I'm really curious about your previous theory - about friction with the ground being required to increase airspeed. Fascinating - please elaborate.

Does the space shuttle use a jet turbine engine?

LMAO - no. What's your point?

 

[jagec]

This thread (a)delivers, and (b)destroys my faith in humanity.

 

[Don Vito Corleone]

Originally posted by: jagec
This thread (a)delivers, and (b)destroys my faith in humanity.

Coincidentally that also sums up ATOT as a whole.

 

[NanoStuff]

If it's true that a jet engine can defy the laws of physics like some here believe to be the case, maybe the space shuttle SHOULD have it.

 

[HeroOfPellinor]

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

I am picturing a jet aircraft. However, I am interested how the wheels provide a force to the ground that equals the forward force the engines generate...Can you explain that? Because that is what you are implying

The wheels aren't. The conveyer belt is. The air passing over the wing is creating upward thrust, but to actually get the plane off the ground so it can begin using air as friction rather than the landing strip it needs to grip something to pull itself along.

The wing behind the turbine would create lift, but not acceleration.


In the rollerblader analogy. How does the rollerblader get pulled off the treadmill by the RC plane if the wheels never exceed the speed of the treadmill. Imagine instead of slippery wheels, you've got interlocking tractor treads.

 

[Don Vito Corleone]

Originally posted by: HeroOfPellinor

The wheels aren't. The conveyer belt is. The air passing over the wing is creating upward thrust, but to actually get the plane off the ground so it can begin using air as friction rather than the landing strip it needs to grip something to pull itself along.

The wing behind the turbine would create lift, but not acceleration.

In the rollerblader analogy. How does the rollerblader get pulled off the treadmill by the RC plane if the wheels never exceed the speed of the treadmill. Imagine instead of slippery wheels, you've got interlocking tractor treads.

This is a joke, right? Please tell me this is a joke.

 

[Tu13erhead]

Originally posted by: HeroOfPellinor
The air passing over the wing is creating upward thrust, but to actually get the plane off the ground so it can begin using air as friction rather than the landing strip it needs to grip something to pull itself along.

Oh, so wrong.

 

[PurdueRy]

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: PurdueRy

Originally posted by: HeroOfPellinor

Originally posted by: Rogodin2
I think the main problem is that people aren't able to picture the plane moving forward on a treadmill that is moving in the opposite direction.

So, let's make is a little easier and visualize a person (on rollerblades) on a 6' long foot tread mill (treadmill moving in reverse) holding a rope tied to a 1/4 scale RC airplane. Once the RC Plane is started and the engine at wto and the person holding the rope attached to the plane they will be moved forward regardless of how fast the tread mill is moving in reverse. This is because the RC Plane is providing the forward momentum.

Don't know if this helps.

Rogo

Possibly. But I'm not sure that's a valid analogy. If you replace the RC plane with somebody standing on a treadmill, that might be more accurate. The purson on the treadmill couldn't pull the rollerblader forward without some friction.

Does a model rocket need friction to take off?

That's a different form of propulsion. Take a helicopter. It does need friction. Air creates friction...just ask the feather.

Can you run hovering in zero gravity?

I am picturing a jet aircraft. However, I am interested how the wheels provide a force to the ground that equals the forward force the engines generate...Can you explain that? Because that is what you are implying

The wheels aren't. The conveyer belt is. The air passing over the wing is creating upward thrust, but to actually get the plane off the ground so it can begin using air as friction rather than the landing strip it needs to grip something to pull itself along.

The wing behind the turbine would create lift, but not acceleration.


In the rollerblader analogy. How does the rollerblader get pulled off the treadmill by the RC plane if the wheels never exceed the speed of the treadmill. Imagine instead of slippery wheels, you've got interlocking tractor treads.

before believe so strongly in this....draw the FBD

 

[cKGunslinger]

Originally posted by: HeroOfPellinor

The wheels aren't. The conveyer belt is. The air passing over the wing is creating upward thrust, but to actually get the plane off the ground so it can begin using air as friction rather than the landing strip it needs to grip something to pull itself along.

Heh, I see those 3 college Logic classes you bandy about have failed you yet again. :laugh:

Perhaps if you had ditched one and went and played a game of billiards at the pool hall, you would have learned a bit more, like the concept of putting "draw" on the cue - hitting the ball such that it spins backwards, yet travels forward.

But how can that be! According to you, in order for an object to move forward it must have enough grip to pull itself along! Zounds!

Originally posted by: PurdueRy
before believe so strongly in this....draw the FBD

Quick Purdue, ask him how many Physics classes he took in college! That's how he believes all arguments can be resolved. :laugh:

 

[themorningbells]

Is the question essentially: if a plane was able to remain stationary, yet spin up its engines to a speed/thrust output sufficient for ordinary take off, could it then achieve flight?

If that is the question as I understand it, I think that it could get of the ground, but its nose would immediately go slamming back down into the ground because of the huge force being exerted upon it all at once. I think that it having no momentum before building up to such a violent thrust would have a serious impact. I believe it's similar to having your head out a window in a car, and the car accelerating from 0-80 in a span of 30 seconds vs. accelerating from 0-80 instantly. You can phsyically deal with the gradual force against your head in the first scenario, but in the second scenario your neck would snap. Maybe it could somehow be compensated for, but I think realistically (however unrealistic this scenario is), it would be too much force at once to actually maintain any stability of flight. I don't have any sort of in depth knowledge of physics or how planes specifically work, but in my mental visualization of it, that is what would happen.

And sorry if this has been covered, but I only read up to page 6 in this thread.

 

[Rogodin2]

In the rollerblader analogy. How does the rollerblader get pulled off the treadmill by the RC plane if the wheels never exceed the speed of the treadmill. Imagine instead of slippery wheels, you've got interlocking tractor treads.

the wheels exceed the speed of the treadmill because the amount of friction generated is minimal compared to the force pulling the person (the RC plane). The only way the rollerblader wouldn't be pulled forward would be if there was a corresponding headwind to match the forward movement of the RC plane.

Rogo

 

[mchammer]

1000 posts!!!

 

[PurdueRy]

Originally posted by: themorningbells
Is the question essentially: if a plane was able to remain stationary, yet spin up its engines to a speed/thrust output sufficient for ordinary take off, could it then achieve flight?

If that is the question as I understand it, I think that it could get of the ground, but its nose would immediately go slamming back down into the ground because of the huge force being exerted upon it all at once. I think that it having no momentum before building up to such a violent thrust would have a serious impact. I believe it's similar to having your head out a window in a car, and the car accelerating from 0-80 in a span of 30 seconds vs. accelerating from 0-80 instantly. You can phsyically deal with the gradual force against your head in the first scenario, but in the second scenario your neck would snap. Maybe it could somehow be compensated for, but I think realistically (however unrealistic this scenario is), it would be too much force at once to actually maintain any stability of flight. I don't have any sort of in depth knowledge of physics or how planes specifically work, but in my mental visualization of it, that is what would happen.

And sorry if this has been covered, but I only read up to page 6 in this thread.

Woah...we got a new issue....

 

[HeroOfPellinor]

Originally posted by: PurdueRy

before believe so strongly in this....draw the FBD

I don't believe so strongly in this. I might be wrong. But I think the analogy of the rollerblader on the treadmill, on which you're all basing your arguments is wrong.

Take a guy standing on a treadmill wearing street shoes. Now there's a guy standing on the ground infront of him and he pulls the guy on the treadmill using a rope. The guy on the treadmill moves the conveyer belt forward as he's pulled forward. That's the "extra" affect induced on the rollerblader on the treadmill. The wheels aren't being turned any faster than the treadmill, but the treadmill itself is being turned.