Question: Will the plane fly? (warning: nerdy)
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Originally Posted by psoper
Bill, please read my post again and tell me how a plane flies just because it "moves in one direction" without neccesarily accelerating to a speed which exceeds its take-off velocity? You have to assume that it does to defend your statement that it will fly- but that information is NOT GIVEN in the problem statement.
The problem may not give EVERY bit of information, but its fairly obvious that the plane is trying to take off and will attempt to accelerate to the propper air speed to do so. Oh and the fact that the plane is moving forward is implied as well by the fact that its trying to take off. Just because every minute detail isn't included in a problem doesn't make it automatically invalid.
Ok, now given the details that made the problem unsolvable, can we move on to trying to solve it instead of nit-picking over small details that should be assumed from the phrasing anyway?
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Originally Posted by Chrisnonstop
The plane will not fly.
Even though the prop is generating thrust, there is no forward momentum. The forward momentum is what puts wind under/over it's wings.
Think of it this way, if you attached a rope to the tail of the plane and then pushed the engines all the way to max, do you think the plane would just jump up into the air and be anchored to the ground by the rope? No it would not. The props don't generate enough foot lbs of thrust. That's why planes have wings. Now if it were a rocket, then yes it would. Because a rocket doesn't need wings. It's got gobs of thrust to push it through the air.
So the bottom line is (besides me rambling) a plane needs foward momentum to take off. If the tires are spinning, there is no forward momentum. That's why planes have tires, wings, and engines,....to fly. You take just one of those things away and it won't fly (by itself).
A rocket will though.
Ok, there are exceptions. There's that tilt rotor aircraft. The offspray or whatever it is. But it's got the advantage tilting it's rotors and HUGE props. So it is able to lift straight up. That's a bit unconventional. We have to assume we're talking about conventional aircraft.
Ok, somebody shoot me now.
Even though the prop is generating thrust, there is no forward momentum. The forward momentum is what puts wind under/over it's wings.
Think of it this way, if you attached a rope to the tail of the plane and then pushed the engines all the way to max, do you think the plane would just jump up into the air and be anchored to the ground by the rope? No it would not. The props don't generate enough foot lbs of thrust. That's why planes have wings. Now if it were a rocket, then yes it would. Because a rocket doesn't need wings. It's got gobs of thrust to push it through the air.
So the bottom line is (besides me rambling) a plane needs foward momentum to take off. If the tires are spinning, there is no forward momentum. That's why planes have tires, wings, and engines,....to fly. You take just one of those things away and it won't fly (by itself).
A rocket will though.
Ok, there are exceptions. There's that tilt rotor aircraft. The offspray or whatever it is. But it's got the advantage tilting it's rotors and HUGE props. So it is able to lift straight up. That's a bit unconventional. We have to assume we're talking about conventional aircraft.
Ok, somebody shoot me now.
If someone says that the plane isn't generating any lift because its not moving again, please explain WHY the plane isn't moving (having read the above).
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No, the plane will not fly. The plane must have forward momentum to generate the lift (vacuum under wing) necessary to gain altitude. Said plane would be in a constant state of "stall" where it's velocity is not a speed at least capable of creating vacuum under the wing.
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I'll keep coming back to "the plane moves one direction" statement, that does not say it accellerates to take-off speed.
No takeoff speed, no flight.
Accelerate to takeoff speed relative to the air around it, and it will fly.
Both scenarios fall within the possible conditions given in the question.
Fact is, and I guess this is where some people just don't get it- the conveyor/treadmill runway doesn't make a whit of difference, because as you and others have pointed out, the wheels are just bogeys and it doesn't matter what they do, the only thing that matters is the planes velocity relative to the air around it.
If there is a tail wind blowing as fast as the planes take-off speed, it probably won't fly either, but if there is a headwind that fast, the plane can even take off without hardly moving forward- what it comes down to is that its all about the wind, not at all about the wheels.
No takeoff speed, no flight.
Accelerate to takeoff speed relative to the air around it, and it will fly.
Both scenarios fall within the possible conditions given in the question.
Fact is, and I guess this is where some people just don't get it- the conveyor/treadmill runway doesn't make a whit of difference, because as you and others have pointed out, the wheels are just bogeys and it doesn't matter what they do, the only thing that matters is the planes velocity relative to the air around it.
If there is a tail wind blowing as fast as the planes take-off speed, it probably won't fly either, but if there is a headwind that fast, the plane can even take off without hardly moving forward- what it comes down to is that its all about the wind, not at all about the wheels.
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Originally Posted by psoper
If there is a tail wind blowing as fast as the planes take-off speed, it probably won't fly either, but if there is a headwind that fast, the plane can even take off without hardly moving forward- what it comes down to is that its all about the wind, not at all about the wheels.
Exactly how a kite works.
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Originally Posted by EQ Tuning
The argument is that the plane DOES move relative to the air. Since its only applying a thrust force on the air itself to accelerate and the air is relatively stationary, the plane WILL accelerate relative to the air. Since its accelerating relative to the air, it has no problem generating the lift necessary to take off. This is assuming its actually trying to achieve the necessary air speed and that its trying to move forward not backwards. The fact that the treadmill bellow the plane is just spinning the wheels faster doesn't apply any significant forces on the plane itself to counter-act the thrust force being applied to the air by the engines/props.
If someone says that the plane isn't generating any lift because its not moving again, please explain WHY the plane isn't moving (having read the above).
Thanks
If someone says that the plane isn't generating any lift because its not moving again, please explain WHY the plane isn't moving (having read the above).
Thanks
Granted, we're not figuring in the mass of the aircraft on top of wheels being spun backwards and the friction generated between the axles. Ultimately there would be a negative effect on the planes forward momentum. Especially if the treadmill was really fast. The planes wheels would need virtually frictionless bearings/axles to allow the plane to achieve flight.
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eh? this question was pretty easy. i just had a hard time trying to visualize it, but its almost an middle schooler question to figure out.
if he had big airplane wings, i doubt a force will be pushing him up.
if he had big airplane wings, i doubt a force will be pushing him up.
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Originally Posted by [W5]IntoTheWRX
if he had big airplane wings, i doubt a force will be pushing him up.
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Originally Posted by psoper
Fact is, and I guess this is where some people just don't get it- the conveyor/treadmill runway doesn't make a whit of difference, because as you and others have pointed out, the wheels are just bogeys and it doesn't matter what they do, the only thing that matters is the planes velocity relative to the air around it.
After clearing up the the left out details as Pete pointed out, we can see that all the plane needs to take off is the ability to accelerate to propper take-off speed. And as Pete mentions here, the wheels don't have a significant effect on the plane's acceleration. It doesn't matter how fast the treadmill spins because the plane will still move relative to the air around it and accelerate just fine. The treadmill will just be spinning the wheels faster, but since the plane doesn't use the wheels to accelerate, it really doesnt matter (of course this is ignoring any frictional losses that put a force on the plane in the other direction, but these are negligable when compared to the thrust force of the plane's engines that are exerter on the relatively stationary AIR around it).
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Originally Posted by svo+wrx
no at those speed you'd spin a bearing in the wheels and blow up /jk but the roflcopter could fly while on a conveyor belt
and +100 on the rolfcopter, that thing can fly anywhere.....
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no, it wont take off because the plane is only moving relative to the belt. compared to the surround air (which when moving over the wing, creats lift) the plane is standing still
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Originally Posted by MBasile
no, it wont take off because the plane is only moving relative to the belt. compared to the surround air (which when moving over the wing, creats lift) the plane is standing still