Airplane + Conveyor Belt
- Started
- Last post
- 74 Responses
- ribit0
To make it clearer... Assuming a 20kmh headwind, and a 250kmh airspeed requirement for takeoff, the plane takes off with these speeds relative to various things...
No conveyer belt:
Plane relative to air: 250kmh
Plane relative to ground: 230kmhWith conveyer belt:
Plane relative to air: 250kmh
Plane relative to ground: 230kmh
Plane relative to conveyer: 460kmh
- Nairn0
Ribit, where you one of those bright kids in school who often got bad grades simply because you didn't read the question?
The conveyor belt serves to nullify any thrust or effect on/from the plane, therefore, the plane is 'stationary'.
In this scenario, the only way to achieve lift would be: a) if the motion of the conveyor belt itself created some freak bernoulli effect b) the volume of space used to conduct the experiment was restricted and designed such that the thrust from the jets created a pressure differential between the front of the experiment containing the jet and the back, pulling air across the wing surface forcing it to act as designed (imagine the jet sitting inside a tube barely large enough to fit the wings and fins - this, of course, would mean that the jet would hit an immediate vertical limitation - the top of the tube!). Outside, in the real world, the air would be drawn from the entire volume of air in front of the jet, and no pressure differential created - or, at least one too massively weak to do anything.
- ribit0
no, I got good grades in physics, and I've flown a plane.
"The conveyor belt serves to nullify any thrust or effect on/from the plane, therefore, the plane is 'stationary'."
Can you explain just how the conveyer belt is supposed to be nullifying the effect of the thrust on the aircraft?
Things to note:
- the conveyer belt can only have an effect on the plane through its wheels
- the wheels are freewheeling
- the wheels are not used to power the plane forward
- the plane moves forward due to the jet thrust following Newtons Laws: http://en.wikipedia.org/wiki/New…
- Nairn0
"This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction)"
= no forward momentum
= no fluid movement over the wing surface
= no pressure differential
= no lift
- skt0
The actual answer is none of the above.
The universe would simply implode.
- ribit0
You are absolutely correct that forward motion is required, but you are drawing false conclusions on that first point...You haven't explained just how the conveyer belt could have any effect on the planes motion. (it doesnt, apart from requiring a tiny amount of extra thrust to counter the increased wheel rotation speed)
There is forward motion, due to the jet thrust. The backwards motion of the conveyer belt simply makes the wheels spin faster, it doesnt affect the whole thrust/motion of the aircraft.
- skt0
If the plane lands at 300kph onto a conveyerbelt moving backwords at 300Kph would the plane stop moving forwards instantly?
Hmmm?
- determinedmoth0
Nairn and Ribit are both wrong.
Nairn - the jets causing forward thrust has nothing to do with the ground, even if the runway is moving there will be forward thrust and movement. However, the plane will still not take off because there will be a drop in friction due to the runway moving. The plane will move forward, but not fast enough to lift. In all probability it would flip out of control and crash.
- determinedmoth0
If ribit was right, Farnborough Airport wouldn't have wind tunnels to test these things would it?
- ribit0
Any plane has plenty of thrust to overcome the additional drag on the wheel bearings. Remember the air drag is still the same, say 350kmh takeoff speed.
The wheels may be doing equivalent of 700kmh, but thats a tiny factor (its not like the planes takeoff speed has been changed to 700kmh relative to the air), so air drag is unchanged compared to non-conveyer-equipped runways.
- ribit0
"If ribit was right, Farnborough Airport wouldn't have wind tunnels to test these things would it?"
they test backwards-moving-conveyer-belt runways?
- harlequino0
Most likely will not take off.
However, under the right conditions, once the plane reaches the equivalent of 88 m.p.h., it will go back to the year 1955.Particularly if a VW van filled with ornery Lybians is in pursuit.
- determinedmoth0
"If ribit was right, Farnborough Airport wouldn't have wind tunnels to test these things would it?"
they test backwards-moving-con veyer-belt runways?
ribit
(Feb 14 06, 06:46)Of course not, because it wouldn't work!
- determinedmoth0
Our IT guy has a PHD in this shit. I'll ask him.
- jakeyj0
BERNOULLI'S PRINCIPLE!!!
- todelete__20
If a tree falls in the woods and no one is around to see it would a plane traveling 300mph still be able to serve hot ham sammiches at 30,000 feet?!?
- ribit0
"BERNOULLI'S PRINCIPLE!!!"
um, yes... but first lets deal with whether this plane is capable of moving itself forward with thousands of pounds of thrust, and freewheeling wheels...
Why does everyone seem to think planes behave like cars?
- jakeyj0
yes - it could still serve sammiches, but those sammiches would be $12 a pop.
- Nairn0
I take it then, that gravity has no bearing on the subject of this experiment?
Until the plane is weightless (or there are no other forces creating friction on the run surface) the energy used for thrust will be trying to push it off the conveyor... but at the same time, we're pumping in just as much energy to mechanically negate the effect of this thrust and push the plane backwards..
..or am I really missing something?
- determinedmoth0
Why does everyone seem to think planes behave like cars?
ribit
(Feb 14 06, 06:58)I dont. I'm with you, and I just asked the guy next to me with a PHD in physics, who pretty much says the same thing. The plane would move forward, but it wouldn't have enough forward thrust and if it tried to lift it would crash.
Unless it was a harrier jump jet!