Airplane Flight Question - Page 6 - United Bimmer Community

witeshark · 11-30-2005, 10:28 PM

The treadmill belt cancels the plane's forward speed. That means no airflow over the lift surfaces assuming no headwind from weather. Without hurricane headwinds, the plane does not have enough lift effect to fly.

**donald1476** · 11-30-2005, 10:30 PM

I give up.

**delmarco** · 11-30-2005, 10:32 PM

I think the confusement lies within the improper wording of the sentence and lack of necassary information

The answer depends upon what the speeds are referenced to. Let's say that the speed is S, which is greater than the take off speed for the plane and there is no wind. There are three cases:

1. The speeds of the conveyor and that of the plane are both with respect to the ground, this is the assumed case. In this case the plane will take off and the plane will be traveling at 2S with respect to the conveyor.
(understood and agreed, but this was never part of the initial question, when you say conveyer belt it can mean anydirection when you say threadmill it usually implies the belt is moving opposite to direction the plane moving in)

2. The speed of the conveyor is with respect to the ground and the speed of the plane is with respect to the conveyor. In this case the plane will not move with respect to the ground and it will not take off.(agree with you but confusing-"with respect to the ground" in what direction. why not say "the belt is moving opposite with repect to the plane's movement". Too many "repects" donald, tighten it up buddy )

3. The speed of the plane is with respect to the ground and the speed of the conveyor is with respect to the plane. In this case the plane will take off, but the the conveyor will not be moving with respect to the ground...( Totally confusing. too many "repects" and now you say the belt is not moving but the belt has a speed with repect to the plane. I getting that the belt is moving in the same direction the plane is moving in but slower than the plane???unlike in 1. where the belt and the plane's speed are moving in sync and hence creates a speed for the plane that is 2S???)

**delmarco** · 11-30-2005, 10:34 PM

Quote:

Originally Posted by donald1476

I give up.

me 2 buddy!

lol!

goodnight!

**voca** · 11-30-2005, 10:35 PM

listen. the plane will have displacement, and it will have airflow over the wings. the conveyer will not slow the plane a significant amount.

I cannot put this in any simpler terms--the plane will take off, the conveyor will only spin the planes wheels twice as fast, but the plane will be going the normal speed.

delmarco, drop all your physics teachings and think of it logically.

**delmarco** · 11-30-2005, 10:41 PM

Quote:

Originally Posted by voca

listen. the plane will have displacement, and it will have airflow over the wings. the conveyer will not slow the plane a significant amount.

I cannot put this in any simpler terms--the plane will take off, the conveyor will only spin the planes wheels twice as fast, but the plane will be going the normal speed.

delmarco, drop all your physics teachings and think of it logically.

I agree with you man.
but ONLY if you are saying the conveyer belt is moving in the SAME DIRECTION that the plane is going in.
So if the plane is racing down the runway in direction NORTH and the belt is moving in direction NORTH then the plane WILL MOVE and eventually FLY.

however if the Plane is moving NORTH and the Belt is moving AT THE SAME SPEED as the planes wheels but in the OPPOSITE direction SOUTH then the plane WILL NOT MOVE. It will be as if on a threadmill.

I am assuming that the belts speed will always match the plane's wheel speed. If there was a difference between the belts speed and the wheels speed then the situation becomes complicated, but the laws will not change.

**delmarco** · 11-30-2005, 10:43 PM

Also I'm assuming there is a pilot on the plane that is pressing down on the pedal trying to move the plane. but the conveyer belt/threadmill will adjust to ALWAYS match the speed of the wheel.

**komodo** · 11-30-2005, 10:43 PM

Quote:

Originally Posted by komodo

That's what I'm saying.

Everyone saying it won't take off is also assuming the plane isn't moving (and thus no wind for the airfold), however I think the plane IS moving. The wheels are spinning freely, but the engines are exerting thrust in the air, pushing the plane forward from the wings. The wheels are going to spin freely, so in response to the engines pushing the plane forward, they'll be spinning twice as fast, but not exerting force in the opposing direction to stop the aircraft. Therefore it will take off like normal, with MAYBE 1 or 2 miles per hour less speed (so it might take a few more seconds before it takes off), from the friction alone, but the difference of friction on freely spinning wheels (which are DESIGNED NOT to cause drag on the object they're on, which is why they roll....).

Reread this.

**voca** · 11-30-2005, 10:45 PM

ugh, it's useless, delmarco.

take this question to one of your physics professors and I can guarantee you he will look you in the face and tell you with minimal thought that the plane will take off.

witeshark · 11-30-2005, 10:49 PM

Quote:

Originally Posted by voca

listen. the plane will have displacement, and it will have airflow over the wings. the conveyer will not slow the plane a significant amount.

I cannot put this in any simpler terms--the plane will take off, the conveyor will only spin the planes wheels twice as fast, but the plane will be going the normal speed.

delmarco, drop all your physics teachings and think of it logically.

In the original wording, it was specified that the belt (conveyor or other) is stated as cancels the plane's forward speed That alone eliminates airflow lift effect!

**komodo** · 11-30-2005, 10:53 PM

Quote:

Originally Posted by witeshark

In the original wording, it was specified that the belt (conveyor or other) is stated as cancels the plane's forward speed That alone eliminates airflow lift effect!

^^ The original wording didn't say it cancels the speed... it just says the treadmill moves in the opposite direction the same speed.

witeshark · 11-30-2005, 10:56 PM

Well, does the resulting affect give the plane any relative headwind?

**voca** · 11-30-2005, 10:57 PM

witeshark, it does not say that, re-read. all it says is that it moves opposite of the plane at the same speed.

for anyone who still can't comprehend this situation, imagine this scenario.

you have a skate board sitting on a conveyer belt (say it's one of those things they have at airports for lazy people) standing still. you run and jump on the skate board and the same time you land on the board the conveyer starts to move in the opposite direction. the only thing that going to slow down the skateboard is the friction in the wheel bearings (without gravity you'd keep going to the other side with the conveyer still moving under you).

the thrust of two jet engines is more than enough power to compensate for the friction at the wheels. the wheels in sense are just pedistals holding the plane from the ground, and no source of power whatsoever.

**donald1476** · 11-30-2005, 10:58 PM

Quote:

Originally Posted by voca

ugh, it's useless, delmarco.

take this question to one of your physics professors and I can guarantee you he will look you in the face and tell you with minimal thought that the plane will take off.

QFT. The three options I posted was given to me by my grandfather with a PhD in Nuclear physics...

**delmarco** · 11-30-2005, 10:59 PM

Quote:

Originally Posted by komodo

Reread this.

Everyone saying it won't take off is also assuming the plane isn't moving (and thus no wind for the airfold), however I think the plane IS moving.

The wheels are spinning freely, but the engines are exerting thrust in the air, pushing the plane forward from the wings.

Okay...this just made a world of difference. I'll tell you why.

If the conveyer belt is not intellegently designed to match the plane's speed at any moment in time whiles the plane is on the conveyer belt then this is no longer a question of physics but a simple matter of common sense.

Now the question is stating "if a plane if moving faster than an oppossing conveyer belt will the plane take off?" the answer is YES!

or "On the ground is a plane's pre-flight velocity determined by turbine power on the wings or the drive power of the wheels?"
That I do not know. But If the wheels are not "drive" wheels and the conveyer belt is not intellegent enought to track and match the wheel speed then the plane can outspeed the belt and fly.

but then again if the conveyor belt can match and track the plane's speed then the plane will NOT FLY. Simply because the turbine push of the turbine-engine can ONLY be express via the plane's wheel speed since the plane is on the ground.

So Komodo to solve this riddle we need to know MORE about that conveyer belt/table cloth/threadmill device.