NOT TRUE. The tires can be spinning 400 miles an hour and the treadmill can be doing the same backwards, the plane is still going to do what ever speed it wants to, with the exception of drag from bearings. OK I have the perfect analogy.

Put a rollerskate on the treadmill. Turn treadmill on. Tires are rolling foward at 5mph, treadmill is going backwards at 5mph. Skate is stationary.

Can you push the skate towards the front of the treadmill? I bet you can.

 

yes u can but then the treadmill will have to speed up per the mind teaser and the forward progress will cease.

 

Exactly.

According to the original question, the treadmill (which is the length of the runway) matches the speed of the tires,
therefore no forward motion.
No forward motion, no lift.

Yes, the tire speed has absolutely nothing to do with the ability of the plane to take off, but the treadmill is effectively pushing the plane backward at the same speed the engines are trying to move it forward,
therefore it is sitting still.

That's my answer and I'm sticking to it.

phox

 

Okay, after 4 pages I guess I need to weigh in. Try this as an example of what really would happen. There are 3 components at work here.

1. Air Speed
2. Ground Speed
3. Conveyor speed

Here we go. The plane starts its engines and begins throttle up.

1. Air Speed = 5 mph forward
2 Ground Speed = 5 mph
3. Conveyor speed = 5 mph backwards

Now remember the wheels have no "bearing" (no pun intended) on the airspeed speed of an aircraft. Everyone on board? Okay now 1/2 throttle.

1. Airspeed 50 mph
2. Ground speed 50 mph
3. Conveyor speed 50 mph backwards.

Only the wheels & the conveyor have a direct correlation to each other and they cancel each other out. The airspeed is still 50 mph forward. The airspeed is directly correlated to the thrust of the engine to the air, which is NOT connected to the wheels or the conveyor. We will have forward motion independant of the wheels.

Full throttle. This is very important to follow.

1. Ground Speed = 150 mph
2. Airspeed = 150 mph
3. Conveyor speed = 150 mph backwards

The plane rotates & lifts off. The max the wheels are spinning are 300 mph 150+150 but we are still moving forward 150 mph airspeed.

1. Airspeed = 175
2. Ground speed = 175
3. Conveyor Speed = 0

Since we are no longer on the conveyor it stopped. You can now look down and see the little cars and trees, cows look like ants. We took off.

 

sorry chief, 150-150=0

 

That's you're answer and you're RIGHT!!! That plane ain't goin' NOWHERE!!!

Simple physics people...simple physics.

Geico...it's YOUR fault. YOU are the one that said that the conveyor speed would always match the speed of the wheels. If that's the case, then the force of the conveyor pushing the plane BACKWARDS will always equal the force of the engines pushing the plane FORWARDS. It goes back to that whole "for every action there must be an equal and opposite reaction". The action is the jet engines pushing the plane forward. The reaction is the conveyor pushing the plane backwards. Since the conveyor always matches the wheel speed....which is in direct correlation with the thrust of the engine (remember....we said no slip), then the plane can't move.

Go ahead. Admit it. I'm a genius.

 

So the wheels are not spinning?

 

yes, but its not going anywhere. when u run on a tread mill your legs are moving but u arent going anywhere relative to the earth

 

So then the wheels are traveling twice the conveyor speed, which is impossible because the conveyor speed will always equal the wheel speed. You forgot to put "4. wheel speed" in.

 

Look at it this way:

Ground Speed = Air Speed (velocity is velocity whether it's on the ground or in the air)

Wheel Speed = 150 mph
Conveyor Speed = 150 mph (because it always matches wheel speed)

Wheel Speed - Conveyor Speed = Ground Speed

150 mph - 150 mph = 0 mph = Ground Speed = Air Speed

Wheel speed is a product of engine thrust so you cannot separate the two like so many of you are trying to do.

I hope you didn't buy a ticket for that plane because it ain't goin' NOWHERE!!

Now, for the sake of getting this bird off the ground let's put some limitations on this conveyor belt and see what happens. Let's say the conveyor belt has a maximum speed of 150 mph. Using the same logic from above, let's look at the equation with this new limitation.

Ground Speed = Air Speed (because velocity is velocity no matter where it's at)

Now let's say that the wheel speed is 300 mph and see what happens.

Wheel Speed = 300 mph
Conveyor Speed = 150 mph (because I put that limit on it above)

Wheel Speed - Conveyor Speed = Ground Speed

300 mph - 150 mph = 150 mph = Ground Speed = Air Speed

So, if you limit the conveyor the plane can take off. Otherwise, it's grounded.

If THAT doesn't make it clear to you infidels then I don't know what will.

 

geico266 what do u know? your just a dumb gecko

 

No offense, but thats a GREAT way to show your intelligence

Anyway, lets say x=wheel speed. Since conveyor speed=wheel speed, conveyor speed also = x. Let ground speed equal y.

ground speed=Wheel speed-conveyor speed, like rac156 and Hoss said.

y=x-x

y=0

 

I've got to say, I think us No Fly Guys are starting to win out.

 

intelligence, whats that?

 

Think about this... How can the conveyor push anything if its on wheels with ball bearings??? It cant! All it is doing is spinning the wheels. The plane will thrust air, and move forwards, and take off. Those little wheels can spin as fast as they want, and the plane is still going to go because it is using the air to make a forward motion, and not the wheels.


Eric