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SuperFly

Joined: 09 Jul 2003 Location: In the doghouse
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Posted: Wed Dec 26, 2007 4:34 pm Post subject: Hey smart guy... |
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A plane is on a runway.
Except the runway is a conveyor belt.
The conveyor belt is infinitely long.
The conveyor belt is spinning at a speed equal to whatever speed the plane would be moving forward if the conveyor belt were not there.
The conveyor belt is spinning backwards. (The plane is trying to move forwards.)
The plane's engines have infinite thrust/power, and the plane has infinite structural integrity.
The plane is on wheels which work properly.
There is no wind, and there are no forces acting on the plane besides the friction between the wheels and the conveyor belt, and the engines.
There is no time limit.
Can the plane take off? |
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eamo

Joined: 08 Mar 2003 Location: Shepherd's Bush, 1964.
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Posted: Wed Dec 26, 2007 4:37 pm Post subject: |
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Noooo! Not this again!!!
We did this about two years ago. Boiled a lot of brains. Be good to have another go though. Let the new guys go nuts. |
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Underwaterbob

Joined: 08 Jan 2005 Location: In Cognito
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Posted: Wed Dec 26, 2007 4:38 pm Post subject: Re: Hey smart guy... |
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SuperFly wrote: |
A plane is on a runway.
Except the runway is a conveyor belt.
The conveyor belt is infinitely long.
The conveyor belt is spinning at a speed equal to whatever speed the plane would be moving forward if the conveyor belt were not there.
The conveyor belt is spinning backwards. (The plane is trying to move forwards.)
The plane's engines have infinite thrust/power, and the plane has infinite structural integrity.
The plane is on wheels which work properly.
There is no wind, and there are no forces acting on the plane besides the friction between the wheels and the conveyor belt, and the engines.
There is no time limit.
Can the plane take off? |
No. There must be some force to lift the plane. Also this question is a jumbled, incredibly irrelevant mess.
Edit: Unless it's one of those planes with tilting engines. |
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adeline
Joined: 19 Nov 2007
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Posted: Wed Dec 26, 2007 4:45 pm Post subject: |
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dude? you can't have friction without gravity and this also wouldn't even work without air and air pressure. i don't think the premise can even work without adding more forces, cause otherwise the plane would be floating off into the ether, is that taking off? |
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SuperFly

Joined: 09 Jul 2003 Location: In the doghouse
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Posted: Wed Dec 26, 2007 4:50 pm Post subject: |
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L=pn X kdA
where:
L is the Lift,
A is the wing surface area
p is the value of the pressure,
n is the normal unit vector pointing into the wing
k is the vertical unit vector, normal to the freestream direction
The above lift equation neglects the Skin friction forces, which typically have a negligible contribution to the lift compared to the pressure forces. By using the streamwise vector parallel to the freestream in place of in the integral, we obtain an expression for the Pressure Drag Dp (which includes Induced Drag in a 3D wing). If we use the spanwise vector , we obtain the Sideforce Y.
If there is no wind and no other forces other than the friction of the wheels, then the P value in the equation will = zero, causing the equation to = ZERO lift. |
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Underwaterbob

Joined: 08 Jan 2005 Location: In Cognito
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Posted: Wed Dec 26, 2007 5:20 pm Post subject: |
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SuperFly wrote: |
L=pn X kdA
where:
L is the Lift,
A is the wing surface area
p is the value of the pressure,
n is the normal unit vector pointing into the wing
k is the vertical unit vector, normal to the freestream direction
The above lift equation neglects the Skin friction forces, which typically have a negligible contribution to the lift compared to the pressure forces. By using the streamwise vector parallel to the freestream in place of in the integral, we obtain an expression for the Pressure Drag Dp (which includes Induced Drag in a 3D wing). If we use the spanwise vector , we obtain the Sideforce Y.
If there is no wind and no other forces other than the friction of the wheels, then the P value in the equation will = zero, causing the equation to = ZERO lift. |
Don't forget the infinitely powerful engines...
Why does the conveyor belt have to be infinitely long when the plane isn't going anywhere? How would a time limit have any bearing on this question at all? |
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ernie
Joined: 05 Aug 2006 Location: asdfghjk
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Posted: Wed Dec 26, 2007 5:41 pm Post subject: |
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no wind = no air pressure = no lift.
<end of thread> |
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RACETRAITOR
Joined: 24 Oct 2005 Location: Seoul, South Korea
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Posted: Wed Dec 26, 2007 6:05 pm Post subject: |
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I think an infinitely long conveyor belt would be weaker than a much shorter conveyor belt, and eventually the great stresses caused by its length would cause it to snap somewhere along the way, then the plane would race away and take off. |
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Bibbitybop

Joined: 22 Feb 2006 Location: Seoul
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Posted: Wed Dec 26, 2007 6:55 pm Post subject: |
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What if the plane has engines that can propel the plane upwards, like in True Lies? |
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pkang0202

Joined: 09 Mar 2007
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Posted: Wed Dec 26, 2007 7:12 pm Post subject: |
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What if the plane were gripped by the husk?
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ultra
Joined: 09 Nov 2007 Location: Book Han Gook Land Of Opportunity
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Posted: Wed Dec 26, 2007 9:49 pm Post subject: |
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What if Chuck Norris exhaled onto the leading edge of the wings? |
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Faunaki
Joined: 15 Jun 2007
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Posted: Wed Dec 26, 2007 10:02 pm Post subject: |
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You were missed SuperF. |
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johndoe

Joined: 29 Jun 2005
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Posted: Wed Dec 26, 2007 10:42 pm Post subject: , |
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johndoe

Joined: 29 Jun 2005
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Posted: Wed Dec 26, 2007 10:43 pm Post subject: , |
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johndoe

Joined: 29 Jun 2005
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Posted: Wed Dec 26, 2007 10:45 pm Post subject: , |
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