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Old 03-04-2006, 09:30 AM
enipla enipla is offline
Join Date: Jul 2001
Location: Colorado Rockies.
Posts: 11,404
Upon review, I would say this is not an open system, but two closed systems.

Originally Posted by Wikipedia
By contrast, a closed (but not isolated) system can exchange heat and work, but not matter, with its surroundings.
Heat and work are exchanged, but not nearly enough to prevent the plane from taking off.

UNLESS you go to BF#2 wherein you dive into theoretical physics and have a constantly accelerating treadmill. I don’t think that that was the point of the original question.

And, I also think that some folks are thinking about a tread mill that is only big enough to support the plane. Especially those folks that make air-craft carrier references.

I’m talking about a tread mill as long or a bit longer than a runway.

Originally Posted by Cecil
Here's the original question: "A plane is standing on a runway that can move (some sort of band conveyer).
A runway that can move.

Hmmmm….. A runway that can move.

Originally Posted by original question
The plane moves in one direction, while the conveyer moves in the opposite direction.
“The plane moves in one direction” Right. There’s the answer to the poorly worded question. If the plane moves, it can generate lift. There’s the so called Plane on a Treadmill – SOLUTION

The plane takes off. More work, certainly. Nearly impossible to control on the ground as the wheels are spinning at twice the rate they normally would. And the transition would be tricky at best. But if this critter could be built, a plane could take off from it.

Cecil nailed it. Twice.