Plane on Conveyor Belt

[madmike2]

Except....

The plane isn't being forced backwards or held in place by a tie-down of any type. Therefore, once the inherent resistance of the wheel bearings and tires is overcome, the plane should then move forward in a normal acceleration mode. Only the tires will be rotating at the faster ground speed (airplane speed + treadmill speed).

When you try your experiment, don't "throttle back" the airplane to match the treadmill speed, but run it through its normal take-off routine.

 

[Scab]

Dude...

One last try, in honor of MM2:

If a plane sits stationary on a treadmill, and then the treadmill is turned on...Yes, the plane will move in the direction of travel of the treadmill, remaining stationary with the treadmill.

The plane then throttles up, of course, facing a direction oposite of the travel direction of the treadmill... The plane will enact a force against the AIR, and at a certain throttle-applied force, will reach an equilibrium and cease travel in the direction of the treadmill. The wheels of the plane and the treadmill will be going the exact same speed, but in oposite directions.

Then the plane adds power. More throttle. More force is applied against the AIR. This will create a forward movement of the plane. It matters not what the wheels and treadmill are doing. Why? Because the plane is applying thrust agianst the AIR.

As the plane continues to add thrust against the AIR, the plane's forward speed will increase. The wheels and treadmill still don't care.

When the thrust of the plane achieves an adequate forward motion, the air passing over the unique shape of the wings will generate lift. The plane flies. The wheels still don't care. Nor does the treadmill.

The treadmill is still turning. The wheels now will stop turning. The plane continues to fly as long as the thrust is provided against the AIR.

This fact is demonstrated on a large scale by the earth itself. It spins just like the surface of a treadmill. Objects sitting stationary on the earth travel with the earth. But the fact that any plane on the earth ever takes flight proves the validity of thrust against air and lift.

Of course, since the treadmill has no bearing on thrust applied against the air, the plane can actually face in either direction and still gain flight provided the plane can apply enough thrust against the air to adequately provide enough air movement across the wings, which will supply the lift by creating an area of lower pressure above the wing surface.

Also, the forces of wind can sometimes be great enough to cause a plane to lift (take off) without the plane moving in relation to the substrate. That is why the tie them down sometimes.

Mikey! Is that better?

 

[wfooshee]

Rondo, if the plane was propelled by its wheels, then (and ONLY then) you would be correct.

The plane's power source and propulsion are not tied to the treadmill in any way.

Let's do this: Forget the plane. Put yourself on a treadmill, with a harness on you. I have a rope tied to the harness that I can do anything I want with.

I elect to tie it to the trailer hitch of my truck and drive away. How fast does your treadmill have to go to keep you from coming with the truck??

It's the same principle. the plane's propulsion has nothing to do with the treadmill. Its propeller, jets, rockets, whatever, push its body forward regardless of what its wheels are doing. It has NOTHING to overcome. If you crank it up while it's moving backwards, that's no different than taking off with a tail wind. More ground speed, but it can do it.

Now, put that plane on the roof of a car, like one of those old stunt shows, put the car on the treadmill going backwards, and the treadmill can match the car's wheel speed and cause there to be no forward airspeed. That's because the car is wheel-driven.

Hmm, no wonder the speed record guys separate wheel-driven and thrust-driven vehicles into different classes. Different physics!

As to the original concept, the point was not to match the plane to the treadmill, but the treadmill to the plane. Can the treadmill pull the plane backwards fast enough to overcome its forward momentum? Since the plane does not push against the treadmill for its propulsion (as a car would), the treadmill has no effect on it other than wheel bearing friction. The model might have been able to be throttled down to provide only the thrust needed to overcome the wheel friction of an 11mph treadmill, but that wasn't the premise. The premise was can the treadmill prevent airspeed, no matter what? The answer is no, it can't, any more than it could prevent me from pulling you in your harness off with my truck.

 

[twowheelnut]

But what if I flick a big honkin' booger onto the conveyor belt and the planes wheels stick to it? Huh? What then?

 

[Toecutter]

https://www.toothpastefordinner.com/052903/********-on-ice.gif

 

[twowheelnut]

But what if I flick a big honkin' booger onto the ice? Will Gallagher trip on it and break his ***? Huh? What then?

 

[RadioHowie]

Then the plane adds power. More throttle. More force is applied against the AIR. This will create a forward movement of the plane. It matters not what the wheels and treadmill are doing. Why? Because the plane is applying thrust agianst the AIR.

You're right...but your wrong. Force isn't being applied "against the AIR". It's simply force being applied in a direction exactly opposite of the direction needed for the plane to take off. It's thrust...that's all, not what the thrust is directed "against" as if the surrounding air is a solid, invisible wall. Whether the thrust comes from a compressed mass of air being driving backwards by a propeller, a stream of hot exhaust driven at near-sonic speeds out the rear of a jet engine, or a burning mixture of liquid oxygen, nitrogen tetroxide, and hydrogen peroxide coming out of the back of a space shuttle, it's the thrust that matters, not the medium (air) the vehicle is in. Want proof? What does a rocket motor in space push against? The motive force isn't pushing against something to move the rocket...it's simply the thrust by itself.

While air is necessary for a propeller driven plane, which of course creates it's thrust by forcing air in the direction opposite of takeoff, it's NOT because the air mass being moved by the propeller is pushing against the air behind the plane. It's just thrust, whether it's caused by a propeller, jet or rocket engine.

Newton's third law, plain and simple.

 

[Rogue]

Okay,

Lets see how many heads will explode with this:

An airplane that can take off at 55 mph is doing 60 mph forward on a runway.

The air plane has a 60 mph tailwind.

Can it take off?

 

[Scab]

Force isn't being applied "against the AIR".

Uh, with all due respect, Horseshit! The force applied (in this case, by the Prop) is applied against the air, thus creating thrust due to the angle of the prop blades and subsequent direction of forced airflow.

Same way lift works. No air, no lift.

With a prop, no air, no thrust.

Yep, Newton's third law. Prop force applied against air, air forced to move.

 

[Scab]

Okay,Lets see how many heads will explode with this:

An airplane that can take off at 55 mph is doing 60 mph forward on a runway.

The air plane has a 60 mph tailwind.

Can it take off?

Yes, it can take off. It just has to go faster than if it had a headwind or no wind.

Now, are you asking if it will take off while doing sixty mph with a sixty mph tailwind, that is a seperate question. And, if the plane can take off at fifty-five mph, what are the conditions when it can do so?

 

[Rogue]

Okay,Lets see how many heads will explode with this:

An airplane that can take off at 55 mph is doing 60 mph forward on a runway.

The air plane has a 60 mph tailwind.

Can it take off?

Yes, it can take off. It just has to go faster than if it had a headwind or no wind.

Now, are you asking if it will take off while doing sixty mph with a sixty mph tailwind, that is a seperate question. And, if the plane can take off at fifty-five mph, what are the conditions when it can do so?

It can take off with zero wind, a ground speed of 55 mph, an air speed of 55 mph.

The ground speed is 60 mph.

Tailwind is 60 mph.

 

[wfooshee]

Okay,Lets see how many heads will explode with this:

An airplane that can take off at 55 mph is doing 60 mph forward on a runway.

The air plane has a 60 mph tailwind.

Can it take off?

Not at 60mph ground speed, but when it reaches 55mph air speed, up she goes. That would need 115mph ground speed, but so what? It only has to generate enough thrust the get 55mph airspeed. The 60mph tailwind gives you the rest.

If you put wings on a subway train, can it tke off? (Given that nobody is standing on the rail relieving themselves after cleaning shot-up fish from the barrel hanging under the lead balloon that exploded when the hydrogen leaked while flying backwards in an ice storm, said explosion being caused by a sniper's bullet piercing the captain's telescope)

Going to bed now. Dishes done, machine running, FJR safe out of the rain, 16-yr-old asleep.

(Remember this thread? She-e-e-e-e's back!!)

 

[Scab]

Now, everybody knows the wings wouldn't fit in the tunnel.

 

[wfooshee]

Guess we have to use the 'L' in Chicago.

Really. Going to bed. 'Night, all!

 

[Scab]

We should all be banned for this thread. :glare:

 

[Ignacio]

Just for the record because I'm sure some wonder. I didn't close this thread.

I've avoided it because I have the episode on DVR and didn't want to spoil it. You all must have annoyed another admin with what appears in the last page to be drivel. Returning it to closed as I'm sure the other admin had a good reason. <_<