Plane on a treadmill

Ho3n3r said:
:crylaugh: After your post, you're criticising MY logic? Now I've seen it all.
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hahah
OK, two scenarios - the firetruck on treadmill given above, and a radio controlled car on a treadmill.
The car stays still. The firetruck moves when you push it.
What's the difference?
The car is driven by its wheels, the firetruck is driven by something OTHER than the wheels (your hand)

So only way a plane would stand still is if the wheels are the bit pushing it forward.
 
Sinbad said:
HOW WILL THE ****ING TREADMILL KEEP THE PLANE IN ONE SPOT?!
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Doesn't matter if it keeps it in one spot or not - the only thing that matters is the airspeed of the wings. If the airspeed is too low, it won't take off. If the treadmill goes fast enough to reduce the airspeed sufficiently, nothing will be taking off.
 
Sinbad said:
HOW WILL THE ****ING TREADMILL KEEP THE PLANE IN ONE SPOT?!
Click to expand...
I'm assuming you guys mean a magical, hypothetical treadmill that will spin and keep the thing in one spot, like treadmills do to humans. If it doesn't whats the point of introducing it in the scenario? Is it just an obstacle for the plane to move over then past and onto the runway? Hows that different to throwing some dead birds on the runway
 
Ho3n3r said:
Doesn't matter if it keeps it in one spot or not - the only thing that matters is the airspeed of the wings. If the airspeed is too low, it won't take off. If the treadmill goes fast enough to reduce the airspeed sufficiently, nothing will be taking off.
Click to expand...

How does the treadmill reduce the speed?
 
Vegeta said:
I'm assuming you guys mean a magical, hypothetical treadmill that will spin and keep the thing in one spot, like treadmills do to humans. If it doesn't whats the point of introducing it in the scenario? Is it just an obstacle for the plane to move over then past and onto the runway? Hows that different to throwing some dead birds on the runway
Click to expand...

If you're running on a treadmill and I shove you in the back, will you stay in one spot?
 
Sinbad said:
hahah
OK, two scenarios - the firetruck on treadmill given above, and a radio controlled car on a treadmill.
The car stays still. The firetruck moves when you push it.
What's the difference?
The car is driven by its wheels, the firetruck is driven by something OTHER than the wheels (your hand)

So only way a plane would stand still is if the wheels are the bit pushing it forward.
Click to expand...

The thrust and the treadmill is cancelling each other out. Even if you have all the thrust in the world, if the airspeed is too low, it won't be taking off.
 
Sinbad said:
How does the treadmill reduce the speed?
Click to expand...

Good point, actually. I was wrong. Thrust will create forward motion regardless of the treadmill, as the thrust is working against air as well.

The wheels will just be going twice as fast, which has nothing to do with airspeed.
 
Ho3n3r said:
The thrust and the treadmill is cancelling each other out. Even if you have all the thrust in the world, if the airspeed is too low, it won't be taking off.
Click to expand...

How? What force is the treadmill exerting on the plane to cancel out the thrust of the engine?
Remember, the wheels are freely turning - there is no friction there (or negligible at least in proportion to the thrust of the engine)
 
Ho3n3r said:
Doesn't matter if it keeps it in one spot or not - the only thing that matters is the airspeed of the wings. If the airspeed is too low, it won't take off. If the treadmill goes fast enough to reduce the airspeed sufficiently, nothing will be taking off.
Click to expand...

If contact with the ground is so important as to affect the forward thrust of a plane, how do planes continue to fly once they take off? And how do seaplanes generate thrust when in contact with a liquid surface?
 
Ho3n3r said:
Doesn't matter if it keeps it in one spot or not - the only thing that matters is the airspeed of the wings. If the airspeed is too low, it won't take off. If the treadmill goes fast enough to reduce the airspeed sufficiently, nothing will be taking off.
Click to expand...
How does a treadmill affect the forward motion of the plane?

Imagine planes take off by rapidly extending a 100m long pole against a fixed wall.
The plane moves forward relative to the wall.

Do you think a treadmill affects the plane moving forward in this scenario?
 
Sinbad said:
How? What force is the treadmill exerting on the plane to cancel out the thrust of the engine?
Remember, the wheels are freely turning - there is no friction there (or negligible at least in proportion to the thrust of the engine)
Click to expand...

Yeah, see my last post. I wasn't thinking properly.
 
Copied from someone on Facebook....

Take a toy plane to the gym and put it on a stationary treadmill. Hold it steady - your hands are the engines, currently doing no work. Now turn on the treadmill - you're now doing a little work to hold the plane still, but not much (because in the puzzle, the wheels are frictionless). Turn up the treadmill as fast as you like, and walk forwards against it, moving the plane as you go. Your hands, the engines, are moving the plane forwards completely independently of the speed of the treadmill. All that's happening is that the wheels are spinning faster, but that has nothing to do with the plane moving forwards or gaining lift once it's going fast enough. Now take your toy plane home because everyone in the gym thinks you're weird and possibly dangerous.
 
Cray said:
If contact with the ground is so important as to affect the forward thrust of a plane, how do planes continue to fly once they take off? And how do seaplanes generate thrust when in contact with a liquid surface?
Click to expand...

See post #149.
 
saor said:
How does a treadmill affect the forward motion of the plane?

Imagine planes take off by rapidly extending a 100m long pole against a fixed wall.
The plane moves forward relative to the wall.

Do you think a treadmill affects the plane moving forward in this scenario?
Click to expand...

See post #149.
 
Sinbad said:
If you're running on a treadmill and I shove you in the back, will you stay in one spot?
Click to expand...
Guys you guys are defending your stupidity. First of all this hypothetical treadmill doesn't exist you made it up. So in this made up scenario the treadmill does what you want it to.

All im saying is that if your made up treadmill keeps the plane in one spot it's not going to fly. If your treadmill is a mere speedbump in the plane's way that it will merely move right over and down the runway as usual then of cause it will fly. Just like it will simply run over someone's luggage on the runway.

This made up thing is changing to fit your argument
 
Vegeta said:
All im saying is that if your made up treadmill keeps the plane in one spot it's not going to fly.
Click to expand...
But a treadmill can't do that.
It can only change how fast the wheels spin.
The forward speed of the plane remains unchanged.

The plane that takes off with a pole:

The plane will always move at speed x relative to the wall.
The wheels on the treadmill can move at whatever speed y they want to.

All we need is plane speed x for takeoff.
Wheel speed y is irrelevant.
 
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