Originally Posted by orange (Post 5817229)

So you're building a critical flaw into the test. Way to get the answer you want.

Perfect rolling = no slippage

Originally Posted by Sully (Post 5817289)

I'm not a physics guy, and once someone's posts go into more than about 15 words or start using formulas, I go into a brief coma.

However, this treadmill thing sound impossible. Once the jet kicks in, there must be forward movement for the wheels to even begin to move against this imaginary treadmill...meaning there will always be forward movement.

Am I wrong?

Originally Posted by cdcox (Post 5817279)

Perfect rolling = pure slippage.

Originally Posted by MagicHef (Post 5817028)

Who said that?

Originally Posted by cdcox (Post 5817274)

Let's try once more from physics.

The plane is initially at zero velocity. To start moving, it needs to accelerate. The acceleration of the plane a = F/m where F is the force and m is the mass of the plane.

The jet engines are one source of force. They push on the air. It is what makes a normal plane move forward.

To keep velocity zero, we need to keep acceleration zero. In order to do that we need a force that opposes the jet engine. The only place it can come from is the tread mill. The tread mill transmits it's force to the wheel and the wheel to the bearing. If the bearing were frictionless, there would be no force on the airplane from this spinning wheel. But in real life, there is friction. The friction would impart a force something like friction force = m*g*k where k is a friction coefficient. Regardless the friction force is small relative to the force of the jet engines. If it were not, the plane couldn't roll in the first place. The velocity of the wheel has very little to do with the amount of friction in the bearing. You can't spin the wheels fast enough to keep the plane stationary by generating more friction at the wheel. It is like the example of a person holding on to the tow rope.

Originally Posted by MagicHef (Post 5817305)

Of course it's impossible. That's not the point.

Originally Posted by MediaCenterJunkie (Post 5817304)

So since the wheels on the plane are going the same speed traveling forward as the rest of the plane, the question is:

Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to exactly match the speed of the plane, moving in the opposite direction. Can the plane take off?

I changed the word Wheels to Plane.

Thats the real question I guess.

Originally Posted by cdcox (Post 5817321)

Actual wheels could not be spun fast enough to generate enough friction to overcome the thrust of jet engines.

Originally Posted by MediaCenterJunkie (Post 5817304)

So since the wheels on the plane are going the same speed traveling forward as the rest of the plane, the question is:

Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to exactly match the speed of the plane, moving in the opposite direction. Can the plane take off?

I changed the word Wheels to Plane.

Thats the real question I guess.

Originally Posted by bdeg (Post 5817314)

the wheel

Originally Posted by MagicHef (Post 5817328)

No, the wheels can be moving at 5 ft/sec with the treadmill moving at 5 ft/sec in the opposite direction, and the plane will be moving at 0 ft/sec.

Originally Posted by Sully (Post 5817323)

I'm just saying, niether the wheel nor the treadmill would ever move in this scenario...right?