A question...

[L32Projekt]

Exactly... thank you very much. The mystery is solved.

My point about 200MPH groundspeed is in reference to the fact that to get the 100mph airspeed necessary for our theoretical aircraft to gain enough lift for takeoff, the groundspeed would be 200mph (conveyor, opposite direction at the same speed the aircraft is travelling... 1mph airspeed, 1mph opposite direction = 2mph, so 100mph airspeed, 100 mph opposite direction=200mph groundspeed=TAKEOFF!)

Does this make sense?

[4thgenowner]

Put a General Electric GE90-115B turbofan on a cessna and put a treadmill on the fuselage and see what happens.

[3.4 slow to go]

http://en.wikipedia.org/wiki/Groundspeed

then ground speed = aircraft speed = tarmac speed

[dmw319]

[img]graemlins/popcorn.gif[/img]

[98Camaro3.8]

Originally posted by 3.4 slow to go:
http://en.wikipedia.org/wiki/Groundspeed

then ground speed = aircraft speed = tarmac speed

Not if the ground is moving.

[Yaba3800]

i likr burrtitos with cheese and beans

[teal99camaro]

Jesus.. I can see what you guys mean now. The wheel speed doesnt really matter does it? Since the air is not being moved by the conveyer belt, the plane will still move, however, the question contains one fallacy. If the conveyer belt is actually able to match the plane's speed than the movement of the plane is impossible, which is one of the stipulations of the question. But in a real world application, I guess you guys are right.

[98Camaro3.8]

Originally posted by teal99camaro:
If the conveyer belt is actually able to match the plane's speed than the movement of the plane is impossible, which is one of the stipulations of the question.

The conveyor will not stop the movement of the plane. It will move normally because the conveyor imparts to actual force on the airplane.

[L32Projekt]

1 converted, eleventybillion to go... :D

[teal99camaro]

Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by teal99camaro:
If the conveyer belt is actually able to match the plane's speed than the movement of the plane is impossible, which is one of the stipulations of the question.

The conveyor will not stop the movement of the plane. It will move normally because the conveyor imparts to actual force on the airplane. </font>[/QUOTE]I realise now that the wheels have nothing to do with the propulsion of the plane. The question is decietful on purpose. It targets people who think of it as a math problem. they take the physically impossible stipulation in the question and use it as a rule to govern the movement of the plane, but in a real world application, the plane would move. the treadmill doesnt move the air backwards aswell.

[L32Projekt]

The force imparted to the aircraft's wheels is not enough to stop it from accelerating because the thrust &gt; drag at the wheels. That's the only thing I can't prove, as how much of an opposing force does the wheels impart on the plane at 200mph, and how much force do the engines exert? If the engine force &gt; drag, then you have acceleration.

Also, Matt correct me if I'm wrong but as the aircraft accelerates and the speed of the air increases and creates lift (not enough to make the aircraft airborne) doesn't it also relieve the weight of the aircraft from the wheels as well?

As such, with less weight on the wheels = less drag, further minimizing the effect the conveyor has on the wheels?

I think we've got a flyer on our hands, boys! :D

[L32Projekt]

Originally posted by teal99camaro:
</font><blockquote>quote:</font><hr />Originally posted by 98Camaro3.8:
</font><blockquote>quote:</font><hr />Originally posted by teal99camaro:
If the conveyer belt is actually able to match the plane's speed than the movement of the plane is impossible, which is one of the stipulations of the question.

The conveyor will not stop the movement of the plane. It will move normally because the conveyor imparts to actual force on the airplane. </font>[/QUOTE]I realise now that the wheels have nothing to do with the propulsion of the plane. The question is decietful on purpose. It targets people who think of it as a math problem. they take the physically impossible stipulation in the question and use it as a rule to govern the movement of the plane, but in a real world application, the plane would move. the treadmill doesnt move the air backwards aswell. </font>[/QUOTE]Yes, in this case, 1-1 does not equal 0.

[98Camaro3.8]

Originally posted by L32Projekt:
Also, Matt correct me if I'm wrong but as the aircraft accelerates and the speed of the air increases and creates lift (not enough to make the aircraft airborne) doesn't it also relieve the weight of the aircraft from the wheels as well?

Depending on the position of the flight controls, this is correct.

If you push the yoke hard over during the takeoff roll you'll never leave the ground (and you'll bury the prop).

On the other hand, you could do a soft field takeoff. The goal here is to keep weight off the wheels so you don't sink in dirt or something. You start with full nose up elevator and add full power. Very quickly after adding power you'll have enough elevator authority to get the nosewheel off the ground. Release some back pressure to hold the nosewheel off without dragging the tail. You'll still be at a slow airspeed (maybe 15 knots in a 172) with the nose pointing up. This means you'll have a high angle of attack. Now as you continue to accelerate, more and more lift is being created (means less weight on the wheels) and the aircraft will lift off as slow as possible.

[img]smile.gif[/img]

[teal99camaro]

If one has to go by whats in the question, than the plane will not take off. But in a real life application, the plane would def. take off.

If this was on a physics test, the plane taking oiff would not be a correct answer. The question is just misleading.


Matches is the key word in the question. And the treadmill matching the speed of the plane's tires is a physical impossiblity

[98Camaro3.8]

Originally posted by teal99camaro:
If one has to go by whats in the question, than the plane will not take off. But in a real life application, the plane would def. take off.

If this was on a physics test, the plane taking oiff would not be a correct answer. The question is just misleading.

Why are you saying that? It's not true. Going by pure physics, there is no reason the plane would not fly. Real life or not, it will fly.

Originally posted by teal99camaro:
Matches is the key word in the question. And the treadmill matching the speed of the plane's tires is a physical impossiblity

Yes, it is impossible, and that's why no one said it matches the speed of the wheel. ;)