Can the plane take off?

nope. needs the wind over and under the wings to create lift. now in a huge wind tunnel that generates enough wind speed it could
 
It is pretty much a "divide by zero" problem. If you read every word of the problem, the plane can't take off or it violates the initial conditions.

Physically, yes the plane could take off if given a huge treadmill that was moving in either direction and was long enough for a take-off run. But it is the wording of the problem that makes actual movement of the plane impossible, and with no movement, then no take-off.
 
The part that made me "get it"....was to remember the engines are what are moving (pushing for jets, pulling for props) the plane. Makes no difference what or how fast the wheels are going. The engines are still going to move the plane...the wheels can scream like crazy on a treadmill if they want to.
 
ErikE said:
The part that made me "get it"....was to remember the engines are what are moving (pushing for jets, pulling for props) the plane. Makes no difference what or how fast the wheels are going. The engines are still going to move the plane...the wheels can scream like crazy on a treadmill if they want to.
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You are correct in part. But a jet engine can pull and a prop can push..
 
There are some "Technical Contributors" on this thread that are out of their lane.

The treadmill provides equal and opposite force of the forward thrust of the jet engines. Airplanes fly because of the airspeed over the wings. The net airspeed is ZERO. The plane doesn't leave the ground, much less move an inch.
 
ErikE said:
The part that made me "get it"....was to remember the engines are what are moving (pushing for jets, pulling for props) the plane. Makes no difference what or how fast the wheels are going. The engines are still going to move the plane...the wheels can scream like crazy on a treadmill if they want to.
Click to expand...
If get it, is like, hit me in the back of the head with a brick then I get it.

Now I wanna see what she looks like coming off the end of the runway/conveyor.
 
LTD.330 said:
There are some "Technical Contributors" on this thread that are out of their lane.

The treadmill provides equal and opposite force of the forward thrust of the jet engines. Airplanes fly because of the airspeed over the wings. The net airspeed is ZERO. The plane doesn't leave the ground, much less move an inch.
Click to expand...
There is NO connection between the engines and the treadmill. The plane will go forward no matter what the treadmill does. Check the mythbusters link. They did this experiment with a real plane and it took off.
 
jmauld said:
The thrust from the engines doesnt care about the speed of the tires. Nothing on the plane cares about the speed of the tires. That number is meaningless to it taking off. Only speed over ground matters.
Click to expand...
Exactly. Only speed over ground matters. The plane has no speed over ground if the conveyor is maintaining exactly the speed of any forward momentum created by the thrust of the engines.

How many MPH is a car traveling on a dyno with the engine running 3,000 RPMs? ZERO. The car never moves but the wheels/tires are rotating like crazy.
 
LTD.330 said:
There are some "Technical Contributors" on this thread that are out of their lane.

The treadmill provides equal and opposite force of the forward thrust of the jet engines. Airplanes fly because of the airspeed over the wings. The net airspeed is ZERO. The plane doesn't leave the ground, much less move an inch.
Click to expand...
I mean seriously… This is so brainless even a buckeye from the state down south can figure out the answer!
 
tc410 said:
Exactly. Only speed over ground matters. The plane has no speed over ground if the conveyor is maintaining exactly the speed of any forward momentum created by the thrust of the engines.

How many MPH is a car traveling on a dyno with the engine running 3,000 RPMs? ZERO. The car never moves but the wheels/tires are rotating like crazy.
Click to expand...
That would be true for a car which relies on the ground to move. With the plane, it doesn't.
 
jmauld said:
There is NO connection between the engines and the treadmill. The plane will go forward no matter what the treadmill does. Check the mythbusters link. They did this experiment with a real plane and it took off.
Click to expand...
The flaw with the Mythbusters experiment is the assumption that the propeller/jet engine pushes/sucks enough air over the entire surface area of the wing to create lift while ignoring the weight required for the additional thrust. P=MV Given the constraints of the original problem, today's planes can't overcome the initial momentum required for takeoff.
 
What? They tested it with an actual plane. They aren’t relying on the engine to push air over the wings. The engines are pushing the planes forward because there is NOTHING stopping the plane from moving forward. The moving surface has no effect on the ability of the engines to move the plane forward, other than the minuscule force required to overcome the friction in the wheel bearings.

You can try this experiment yourself.

Take a wagon and load it with 100lbs. Set it on a moving treadmill and take note of how little force it takes for you to hold the wagon steady. Now push the wagon forward with the treadmill still moving. You’ll have no problem overcoming the friction of the wheels. Take it off the treadmill and set it on the ground. You’ll find it takes about the same amount of force to move it on stationary ground.

That’s the same relationship to a jet engine moving a plane. The engine just doesn’t give a shit about the treadmill and how fast it’s going. It’s going to move that plane forward just like it normally would.
 
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I think the “problem” with the Mythbusters test is that the weight of the plane will allow the wheels to still have “contact” with the ground. It is impossible to truly test this as it is impossible to have a conveyor belt suspended so the weight of the plane is only carried by the belt.
 
It’s not a problem though because it doesn’t matter. The wheels on the plane are free spinning and their speed doesn’t effect the thrust of the engines.
 
LTD.330 said:
There are some "Technical Contributors" on this thread that are out of their lane.
The treadmill provides equal and opposite force of the forward thrust of the jet engines. Airplanes fly because of the airspeed over the wings. The net airspeed is ZERO. The plane doesn't leave the ground, much less move an inch.
Click to expand...
tc410 said:
I mean seriously… This is so brainless even a buckeye from the state down south can figure out the answer!
Click to expand...
The treadmill spins the aircraft's wheels. If the wheel bearings were frictionless the aircraft would not move regardless what the treadmill and wheels are doing. Agree? The "equal and opposite force" as you point out is isolated between the wheels and treadmill; nothing else have forces imposed (sans friction and inertial forces due to the mass of the wheels).

So from the "Brainless" Technical Contributor -

If the aircraft moves forward at 10 miles per hour using it's engines the wheels rotate (say) at 50 RPM without the treadmill moving. Then the treadmill counters that wheel rotation the wheels now rotate at 0 RPM. But, the aircraft still moves forward at 10 miles per hour. At this point the aircraft and treadmill are both moving forward at 10 miles per hour and the wheels are not turning at all.

So the aircraft is now at 120 miles per hour (forward speed = air speed) powered by it's engines and creating enough lift at the wings to take off and the wheels would spin at 500 RPM without a treadmill. With a treadmill countering the wheel RPM the wheels are now spinning at 0 (zero) RPM but the aircraft is still traveling at 120 miles per hour creating enough lift at the wings and taking off.

Now let's look as if the treadmill is spinning the wheels the same direction rather than counter - the aircraft is moving forward and wheels are spinning at 50 RPM then the tread mill adds 50 RPM resulting in wheel speed of 100 RPM but, lo and behold, the aircraft is still moving forward.....
Class is dismissed....
 
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ttmott said:
The treadmill spins the aircraft's wheels. If the wheel bearings were frictionless the aircraft would not move regardless what the treadmill and wheels are doing. Agree? The "equal and opposite force" as you point out is isolated between the wheels and treadmill; nothing else (sans friction and inertial forces due to the mass of the wheels) have forces imposed.

So from the "Brainless" Technical Contributor -

If the aircraft moves forward at 10 miles per hour using it's engines the wheels rotate (say) at 50 RPM without the treadmill moving. Then the treadmill counters that wheel rotation the wheels now rotate at 0 RPM. But, the aircraft still moves forward at 10 miles per hour. At this point the aircraft and treadmill are both moving forward at 10 miles per hour and the wheels are not turning at all.

So the aircraft is now at 120 miles per hour (forward speed = air speed) powered by it's engines and creating enough lift at the wings to take off and the wheels would spin at 500 RPM without a treadmill. With a treadmill countering the wheel RPM the wheels are now spinning at 0 (zero) RPM but the aircraft is still traveling at 120 miles per hour creating enough lift at the wings and taking off.

Now let's look as if the treadmill is spinning the wheels the same direction rather than counter - the aircraft is moving forward and wheels are spinning at 50 RPM then the tread mill adds 50 RPM resulting in wheel speed of 100 RPM but, lo and behold, the aircraft is still moving forward.....
Class is dismissed....
Click to expand...

EXACTLY! There is no significant "force" opposing the thrust, the friction in the bearings and tires is minimal compared to the thrust capability. It would violate the three Newtons laws of motion otherwise.
 
ttmott said:
The treadmill spins the aircraft's wheels. If the wheel bearings were frictionless the aircraft would not move regardless what the treadmill and wheels are doing. Agree? The "equal and opposite force" as you point out is isolated between the wheels and treadmill; nothing else (sans friction and inertial forces due to the mass of the wheels) have forces imposed.

So from the "Brainless" Technical Contributor -

If the aircraft moves forward at 10 miles per hour using it's engines the wheels rotate (say) at 50 RPM without the treadmill moving. Then the treadmill counters that wheel rotation the wheels now rotate at 0 RPM. But, the aircraft still moves forward at 10 miles per hour. At this point the aircraft and treadmill are both moving forward at 10 miles per hour and the wheels are not turning at all.

So the aircraft is now at 120 miles per hour (forward speed = air speed) powered by it's engines and creating enough lift at the wings to take off and the wheels would spin at 500 RPM without a treadmill. With a treadmill countering the wheel RPM the wheels are now spinning at 0 (zero) RPM but the aircraft is still traveling at 120 miles per hour creating enough lift at the wings and taking off.

Now let's look as if the treadmill is spinning the wheels the same direction rather than counter - the aircraft is moving forward and wheels are spinning at 50 RPM then the tread mill adds 50 RPM resulting in wheel speed of 100 RPM but, lo and behold, the aircraft is still moving forward.....
Class is dismissed....
Click to expand...
This
 
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