Skill's weekend teaser

This is a discussion on Skill's weekend teaser within the General Trading Chat forums, part of the Reception category; Originally Posted by Skill Leverage OK, Bramble: The conveyor belt merely causes the wheels to spin, frictionlessly, on their axels. ...

View Poll Results: What will happen?
The plane will take off normally 25 40.32%
The plane will remain stationary 32 51.61%
The plane will run out of conveyor belt before it can take off 5 8.06%
Voters: 62. You may not vote on this poll

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Old Feb 22, 2009, 3:34pm   #127
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Quote:
Originally Posted by Skill Leverage View Post
OK, Bramble:

The conveyor belt merely causes the wheels to spin, frictionlessly, on their axels. The plane does not move in any way due to this. It only moves when the engine is switched on.

Say the belt is moving at a billion miles an hour. The wheels are, in turn, spinning at a billion miles an hour (rotational speed.)

THE NET FORCE ON THE PLANE IS ZERO - the wheels are spinning on their axes, the plane is not moving at all.

Now, the engines are switched on - THE NET FORCE ON THE PLANE BECOMES POSITIVE - the plane takes off!!!!
WHAT!!! This is not the detail in post #1. Which one are we solving for? The original one or this new one?
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Old Feb 22, 2009, 3:36pm   #128
 
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Skill Leverage started this thread The key point, by the way, in new_trader's post is, the car is not in gear. This is exactly the same for these purposes as a plane whose wheels do not create forward motion.

Please get this through your bloody skull so I can go and cry in my pillow.
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Old Feb 22, 2009, 3:36pm   #129
 
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Skill Leverage started this thread
Quote:
Originally Posted by TheBramble View Post
WHAT!!! This is not the detail in post #1. Which one are we solving for? The original one or this new one?
YES IT BLOODY IS! WHAT SORT OF PLANE DO YOU KNOW THAT DRIVES THROUGH ITS WHEELS???

AAAAAAAAAAARGH
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Old Feb 22, 2009, 3:36pm   #130
 
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Originally Posted by Lightning McQueen View Post
you can't leave, I haven't finished me popcorn yet!
Think skills gonna pop his corn in a moment !!!
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Old Feb 22, 2009, 3:37pm   #131
 
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Skill Leverage started this thread Fair enough I didn't mention that the wheels are frictionless, but it doesn't really matter; even if there were friction, the plane still takes off once it has overcome this! New_trader explained it perfectly.

Please tell me the penny has dropped and I can go...
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Old Feb 22, 2009, 3:38pm   #132
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Originally Posted by Skill Leverage View Post
Imagine a 747 sitting on a very large conveyor belt. The belt has the same dimensions as a runway at an airport*, and is set up to exactly match the speed of the plane's wheels, moving in the opposite direction.
|So, let's pretned the wheels are merely used to determine the speed of the plane over the surface of the conveyor. If the conveyor is always moving at the same speed, but in an opposite direction to the wheels, regardless of the speed, the net forward motion of the plane relative to the ground upon which the conveyor is standing is 0 mph. Have I got that right?

If I have, where does the 180 mph breeze necessary to provide sufficient lift to loft the bastie upward come from?
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Old Feb 22, 2009, 3:38pm   #133
 
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Going to quote what I said in the previous teaser thread:

Quote:
I'm eagerly awaiting the sh*tstorm that the "plane on a treadmill" will generate
Skill Leverage is correct, the plane will take off. The reason people seem to struggle with this problem is that they assume that the moving conveyer belt is providing a force opposing the plane's foward movement. In reality, the force created by the conveyer belt only acts on the wheels, and since the wheels can move completely independently of the plane, the force from the conveyer belt doesn't affect the plane. Obviously this assumes the wheels can spin freely without friction - stick the brakes on and the conveyer belt will be able to exert a force on the plane as a whole.
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