Plane on a Treadmill

[singsing]

I agree, you need sleep because that doesn't make any sense.

Because as you've stated, once you have enough thrust to overcome weight it doesn't matter if the wheels are spinning under you. It really doesn't matter if the planes on its tail, it will move forward if enough thrust is given. Good night.

 

[herbicide]

Here is where your post falls apart. The treadmill is not providing any meaningful energy to the plane through the wheels. As we've been over a dozen times, the wheels on a plane are meant only to rotate to support the plane as it is pushed forward. The moving treadmill, and therefore the moving wheels do not transfer this energy to the plane. The jets of the plane aren't overcoming the treadmill, the treadmill means nothing.

The jet engines create thrust, and push the plane, on solid ground, the wheels only spin the same speed the plane is moving as a result of the thrust. Now add the treadmill, the wheels spin faster to accommodate for the ground which is now in motion, but since the wheels of a plane are not driving said plane and are instead just spinning freely, the plane does not jolt to a stop, it takes off as normal.

But there is FRICTION between the wheels and treadmill. The faster the wheels spin, the more friction, and hence the more energy to overcome this friction. Otherwise, the plane would just follow the belt. Try to step on to a moving treadmill and you will learn this law of physics.

While you are at it, read the principles of an airfoil (wing).

 

[jbhtexas]

Jet engines, as well as propeller "engines" use pressure differential to apply power or force, IE they create a low pressure area and a high pressure area. This is what causes them to apply power/force, ie high pressure area vs. low pressure area = high pressure area moves to low pressure area to equalize force.

They adhere to the same laws of physics as any other engine.

Thrust (or Force) = mdot * delta V., which is

(mass flow rate of air/gas)
times
(the air/gas velocity at the outlet of the device minus the air velocity at the inlet of the device).

For propellers, mdot is large and delta V is small, i.e. a large volume of air is moved, but the velocity increase of the air is not large.

For turbojets, mdot is small, but delta V is large, i.e. the mass flow rate of air is smaller relative to the propeller, but the velocity change is very large.

 

[herbicide]

Here is where your post falls apart. The treadmill is not providing any meaningful energy to the plane through the wheels. As we've been over a dozen times, the wheels on a plane are meant only to rotate to support the plane as it is pushed forward. The moving treadmill, and therefore the moving wheels do not transfer this energy to the plane. The jets of the plane aren't overcoming the treadmill, the treadmill means nothing.

The jet engines create thrust, and push the plane, on solid ground, the wheels only spin the same speed the plane is moving as a result of the thrust. Now add the treadmill, the wheels spin faster to accommodate for the ground which is now in motion, but since the wheels of a plane are not driving said plane and are instead just spinning freely, the plane does not jolt to a stop, it takes off as normal.

But it does not take off! If the speed of the treadmill equaled the speed of the plane, how did the plane ever advance on the treadmill? Keep in mind it NEVER took off!

 

[cmoneyr]

But there is FRICTION between the wheels and treadmill. The faster the wheels spin, the more friction, and hence the more energy to overcome this friction. Otherwise, the plane would just follow the belt. Try to step on to a moving treadmill and you will learn this law of physics.

While you are at it, read the principles of an airfoil (wing).

We've been over the difference between a plane on a treadmill and a person stepping on one. If I was wearing rollerblades and got on a treadmill I would be stationary assuming no outside forces, I would not fall off.

 

[cmoneyr]

But it does not take off! If the speed of the treadmill equaled the speed of the plane, how did the plane ever advance on the treadmill? Keep in mind it NEVER took off!

The treadmill could triple the speed of the plane or more and it wouldn't matter. The treadmill would run faster, and the wheels, which are there only to spin and support the plane, would rotate even faster to accommodate for the amount of thrust and the speed of the treadmill. Assuming the wheels had no maximum speed it wouldn't matter how fast the treadmill was going, the only thing that matters is the amount of thrust.

As the treadmill went faster than the thrust the friction would obviously be greater and more thrust would be needed. But since we're talking about matching speeds, the amount of friction would be negligible compared to the amount of thrust produced by a jet engine.

In summation, the plane takes off.

 

[herbicide]

Re: CyBookie - Plane on a Treadmill

Are you serious? This is the most idiotic thing I have ever heard. The plane with have no wind moving across its wings, no wind = no lift = no flight. That plane will 100% NOT take off. We need an event on it, cause I am going all in, and begging Jeremy for a $1M credit loan to go all in on that!

Me too. All in. I will even throw all my worldly assets into this for real $$$

 

[herbicide]

We've been over the difference between a plane on a treadmill and a person stepping on one. If I was wearing rollerblades and got on a treadmill I would be stationary assuming no outside forces, I would not fall off.

FRICTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

OK, Little experiment to prove the existence of friction. Set a roller blade on a moving treadmill. Notice a force you must apply to keep it in place? I know it may not be much, but it is there. Now let it go. What happens?

 

[singsing]

We've been over the difference between a plane on a treadmill and a person stepping on one. If I was wearing rollerblades and got on a treadmill I would be stationary assuming no outside forces, I would not fall off.

Good comparison. Why are you still doing this to yourself?

 

[cmoneyr]

But it does not take off! If the speed of the treadmill equaled the speed of the plane, how did the plane ever advance on the treadmill? Keep in mind it NEVER took off!

Oh, and please read the examples already stated in the thread, around page 8ish. the treadmill is a red herring in this problem.

 

[cmoneyr]

FRICTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

LOUD NOISES!!!!!!!!!!!!!!

 

[cmoneyr]

You think the friction of the wheels is enough to counter act the thrust of the jet engine? Those are some crappily designed wheels.

 

[jbhtexas]

But there is FRICTION between the wheels and treadmill. The faster the wheels spin, the more friction, and hence the more energy to overcome this friction. Otherwise, the plane would just follow the belt. Try to step on to a moving treadmill and you will learn this law of physics.

While you are at it, read the principles of an airfoil (wing).

Again, stepping on a treadmill is not germain to this issue. Once the plane overcomes the initial force of static friction, the force of rolling friction is significantly less.

The process by which airfoils create lift is not the issue here. Nobody is disputing that the airplane has to achieve a certain velocity so that the air flowing over the airfoil will create enough upward force to lift the plane off the ground.

 

[cmoneyr]

Let me try this scenario:

Take a shopping cart, a treadmill and a length of rope. Tie the rope to one end of the shopping cart, like you were pulling it behind you. Put the cart on the treadmill and turn it on with the rope slacked. The cart would be stationary, the wheels of a shopping cart do not produce and power and are there only to spin as the pusher provides thrust.

So we have a cart on a moving treadmill, just sitting there. Now take the rope and begin to pull on the cart, does the cart remain stationary? No, the wheels spin at an increased rate based on the speed you pull and the speed of the treadmill. Since the wheels do not factor into how fast a shopping cart moves, the cart moves forward with an increased wheel speed.

Now, double/triple/quadruple the speed of the shopping cart as you are still pulling on the rope. Does the increased speed stop you from being able to pull the shopping cart forward? No, once again, the wheels spin faster and faster, (I'm assuming for this that the wheels won't fall apart), but no matter how fast they spin the cart will only move forward equal to the amount of force you are pulling the rope.

Now, if we replace the shopping cart with a plane, the plane only needs to be able to move forward to make air pass over the wings and therefore create lift. Since the plane/shopping cart will move forward how ever fast you pull it/however fast the jets propel it, the plane will take off as normal.

I'll repost this now that herbicide has joined the fun.

 

[herbicide]

Again, stepping on a treadmill is not germain to this issue. Once the plane overcomes the initial force of static friction, the force of rolling friction is significantly less.

The process by which airfoils create lift is not the issue here. Nobody is disputing that the airplane has to achieve a certain velocity so that the air flowing over the airfoil will create enough upward force to lift the plane off the ground.

But friction is still present! The treadmill removes the aerodynamic drag away from the equation. it can now ignore the forces of aerodynamic drag. This is why it can accelerate to a speed beyond what it could on stable ground.

Test by holding a rollerblade on a moving treadmill. Yes, less friction then a boot, but still takes some effort to keep it in place. Now let go of rollerblade. What happens? Do same experiment with car, put in neutral going down a flat highway. What happens?

I will challenge all and any takers to an approved. scientific experiment on this. Seriously. All odds taken.

 

[herbicide]

I'll repost this now that herbicide has joined the fun.

Yes, but the faster it goes, slower the same force is able to accelerate it. Same reason your car can go 0-30 in less time than it can go 60-90.

Bedtime folks,

Read up on physics while I sleep.

 

[cmoneyr]

But friction is still present! The treadmill removes the aerodynamic drag away from the equation. it can now ignore the forces of aerodynamic drag. This is why it can accelerate to a speed beyond what it could on stable ground.

I will challenge all and any takers to an approved. scientific experiment on this. Seriously. All odds taken.

You and friction need to get a room. The amount of any friction present between the wheels and the treadmill is going to be so small in relation to the amount of thrust produced by a plane that it wouldn't matter. There's also friction when a plane takes off on solid ground, but I assume it's still able to get in the air.

 

[jbhtexas]

But there is FRICTION between the wheels and treadmill. The faster the wheels spin, the more friction, and hence the more energy to overcome this friction.

I disagree.

The rolling friction force = Cf * Fn.

Fn is the normal force which is generally the weight of the supported object.

Cf is the coefficient of friction, and is defined for various surfaces of contact.

Cf in itself is not dependent on the rotational speed of the tire. However, Cf can be affected by temperature of the contact surfaces. As the wheels spin faster, the tires heat up, and Cf may increase. If the tires are effective at dissipating the friction energy, Cf will not appreciably change as the tires spin faster, and the rolling resistance will not increase with rotation speed.

 

[herbicide]

You and friction need to get a room. The amount of any friction present between the wheels and the treadmill is going to be so small in relation to the amount of thrust produced by a plane that it wouldn't matter. There's also friction when a plane takes off on solid ground, but I assume it's still able to get in the air.

Which is exactly why the plane in youtube accelerated so fast, (in comparison to treadmill) yet never left the ground.

 

[herbicide]

I disagree.

The rolling friction force = Cf * Fn.

Fn is the normal force which is generally the weight of the supported object.

Cf is the coefficient of friction, and is defined for various surfaces of contact. Cf in itself is not dependent on the rotational speed of the tire. However, Cf can be affected by temperature of the contact surfaces. As the wheels spin faster, the tires heat up, and Cf may increase. If the tires are effective at dissipating the friction energy, Cf will not appreciably change as the tires spin faster, and the rolling resistance will not increase with rotation speed.

Calculate the wheel bearing friction as well and you are getting close...

Then read up again on the principles of an airfoil (wing) and I will see you all tomorrow.