The Art

[Overread]

The plane moved forward past the cones - along the runway. The whole point is that the plane remain stationary in relation to the ground due to the conveyor counteracting the plane's forward thrust.

You are missing the point.... It is impossible for a conveyor belt to keep the plane stationary.

they just need a bigger, faster truck to pull it

 

[Buckster]

You don't get a plane into the air without lift. You don't get lift without airflow over the wings. You don't get airflow over the wings unless the plane is moving forward in relation to the air.

What moves the plane forward? Jet propulsion which only acts on the fluid surrounding not the ground (or conveyor belt) which is isolated from the plane itself. You said it yourself... "moving forward in relation to the air". Conveyer belt does not act on the air.


What you say is only true if and only if the forward motion of plane is achieved via applying force to the rotation of the wheels just like a car.

I see what you're saying now and, as counter-intuitive as it first seems, you're right.

That's awesome. :thumbup:

 

[usayit]

Airplane on a Conveyor Belt Tempus Fugit by Mark Jaquith

"The problem here, of course, is that the poster (and Neal) cannot disengage themselves from seeing the airplane as a car. The difference between a car and a grounded airplane is that a car uses its wheels to propel itself forward, and an airplane moves itself forward by moving air. They assume that the runway moving backwards would move the plane backwards. This is what would happen with a car (that is in gear), so why not for an airplane? Well, because an airplane’s wheels are free rolling. There is obviously some friction, so there would be some small backwards force, but it would be infinitely small as compared to the forward thrust of the airplane."

 

[usayit]

I see what you're saying now and, as counter-intuitive as it first seems, you're right.

Most Myths are counter-intuitive... that's what makes them interesting.

Here's another:

If I drop a bowling ball and a feather at the same time on the moon (vacuum), which will hit ground first?

 

[Buckster]

They hit at the same time. I think Apollo actually conducted that experiment, but with a feather and a rock instead of a bowling ball?

 

[usayit]

Ah.. yup... do you know why?

 

[Overread]

They should hit at the same time because nothing stops the feather falling like on earth - so in a perfect vacuum its gravity alone that pulls one down and defines the terminal velocity - whilst in a partial or full atmosphere resistance might cause small or major differences in the resulting terminal velocity.

edit (yay I think I remembered some physics for once!!)

edit 2 - wait its only school level - that means its all lies!!

 

[usayit]

Oh.. but hold on... (just adding to the confusion)

Newtonian Mechanics state:

Kinetic Energy = 1/2 (mass) (velocity)^2

If the mass of the bowling ball is greater than feather then why not?


(btw .. you are right... just more talk to hit page 42 )

 

[Overread]

wait wait I know this one - its because the ball and feather arn't falling down its the earth moving up (or in the moons case the moon) to meet the ball and feather - so the mass of the earth is a constant and singular so there is only one kinetic force!

(I might be totally making this one up though )

 

[usayit]

Hint....

Inertia

 

[KmH]

I was on one board that went 64 pages discussing whether an airplane could take off if it was on a conveyor belt that matched (in reverse sense) the movement of the wheels. Anyone know what I'm talking about?

There's enough content to discuss that for 64 pages?

Its all about Bernoulli's principle .. the conveyor belt is irrelevant.

OK, let's try this:

Imagine you've got a plane sitting on a runway. This runway, however, is special - it's a conveyor belt that senses the motion of the airplane's wheels. So, as soon as the airplane starts its engines and gets enough thrust to move the wheels, the conveyor belt senses this movement and rolls back the same amount that the wheels move forward. Will this plane ever leave the ground? (for purposes of this discussion, assume all frictional effects of wheels, tires, and conveyors, are null).

No it won't, because without sufficient air movement over the wings from forward motion of the airplane, no lift is generated because there is no pressure differential, which is what Bernoulli's principle is all about.

Bernoulli's principle - Wikipedia, the free encyclopedia

There is a special case of Bernoulli's principle that was investigated for a time and was know as WIG, or a wing in ground effect. Ground effect vehicle - Wikipedia, the free encyclopedia

In the case of a airplane having engine driven propellers in front of the wings, they cannot move air over enough of the wings surface area to generate the lift required for the airplane to take flight. The angle of attack of the wing is critical for it's performance, particularly at takeoff. A wing is shaped differently by the flaps and/or slats, for takeoff and landing than for flight at normal cruising speeds.

In fact, in flight the area of the wing shielded by the propellers delivers less lift than the portion of the wing not shielded by the propellers.

Wing - Wikipedia, the free encyclopedia

 

[Buckster]

Ah.. yup... do you know why?

I'm old, but as I recall...

Gravity acts on everything in the same way, with the same force. You need something to counteract it to make any difference.

On Earth (relative to this experiment in physics), air acts as a fluid that the two objects need to 'sink' through. The bowling ball's mass outmatches the air's by so much, it has no problem at all bullying it's way through to get to the bottom. The feather's mass is much closer to that of the air's so it has a harder time pushing against it, which slows it's rate of decent.

On the moon, there is so little in the way of atmosphere that it doesn't effectively play a role as a counteracting force.

 

[DennyCrane]

But, if bears eat oats and does eat oats, do little lambs still eat ivy?

 

[Josh66]

There's enough content to discuss that for 64 pages?

Its all about Bernoulli's principle .. the conveyor belt is irrelevant.

OK, let's try this:

Imagine you've got a plane sitting on a runway. This runway, however, is special - it's a conveyor belt that senses the motion of the airplane's wheels. So, as soon as the airplane starts its engines and gets enough thrust to move the wheels, the conveyor belt senses this movement and rolls back the same amount that the wheels move forward. Will this plane ever leave the ground? (for purposes of this discussion, assume all frictional effects of wheels, tires, and conveyors, are null).

No it won't, because without sufficient air movement over the wings from forward motion of the airplane, no lift is generated because there is no pressure differential, which is what Bernoulli's principle is all about.

Bernoulli's principle - Wikipedia, the free encyclopedia

There is a special case of Bernoulli's principle that was investigated for a time and was know as WIG, or a wing in ground effect. Ground effect vehicle - Wikipedia, the free encyclopedia

In the case of a airplane having engine driven propellers in front of the wings, they cannot move air over enough of the wings surface area to generate the lift required for the airplane to take flight. The angle of attack of the wing is critical for it's performance, particularly at takeoff. A wing is shaped differently by the flaps and/or slats, for takeoff and landing than for flight at normal cruising speeds.

In fact, in flight the area of the wing shielded by the propellers delivers less lift than the portion of the wing not shielded by the propellers.

Wing - Wikipedia, the free encyclopedia

So, what exactly do you propose is stopping the plane from moving forward? As long as the brakes are off, the plane will move (and become airborne).

The ground speed doesn't matter. Air speed does.

 

[usayit]

There's enough content to discuss that for 64 pages?

Its all about Bernoulli's principle .. the conveyor belt is irrelevant.

OK, let's try this:

Imagine you've got a plane sitting on a runway. This runway, however, is special - it's a conveyor belt that senses the motion of the airplane's wheels. So, as soon as the airplane starts its engines and gets enough thrust to move the wheels, the conveyor belt senses this movement and rolls back the same amount that the wheels move forward. Will this plane ever leave the ground? (for purposes of this discussion, assume all frictional effects of wheels, tires, and conveyors, are null).

No it won't, because without sufficient air movement over the wings from forward motion of the airplane, no lift is generated because there is no pressure differential, which is what Bernoulli's principle is all about.

Bernoulli's principle - Wikipedia, the free encyclopedia

There is a special case of Bernoulli's principle that was investigated for a time and was know as WIG, or a wing in ground effect. Ground effect vehicle - Wikipedia, the free encyclopedia

In the case of a airplane having engine driven propellers in front of the wings, they cannot move air over enough of the wings surface area to generate the lift required for the airplane to take flight. The angle of attack of the wing is critical for it's performance, particularly at takeoff. A wing is shaped differently by the flaps and/or slats, for takeoff and landing than for flight at normal cruising speeds.

In fact, in flight the area of the wing shielded by the propellers delivers less lift than the portion of the wing not shielded by the propellers.

Wing - Wikipedia, the free encyclopedia

Answer is in the thread.... so is the experiment.