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That might be the case, but the evidence y"all offer is partly erroneous, and partly requires faith. I should not longer say that y"all are completely wrong. I"m not entire certain either way at this point. Your free body diagram is missing some key forces: Friction between the wheels...

Why still all this nonsense about the wheels exerting no force because they are rolling? I brough this up in physics today, and we spent an hour discussing it with a PhD in theoretical physics who has "over 40 years" (his words) experience as a physicist. Also, he is a Nobel Leuraete. I...

No sleep last night. A 104 degree fever on Saturday fubar"d my sleep schedule... Just explaining why I"m here. Just thought it might be an interesting aside for ya that you"re right about the bike. It would fall away from the wall unless dropped straight down, parallel to it. You even...

You"re thinking three dimensionally, not four dimensionally. I"ll use a shopping cart as an example. When you push a shopping cart, you are what is moving the cart, right? Wrong. You push on the cart, and the wheels turn with a momentum equal to the mass of the cart times the velocity with...

Yes, but the wheels support the plane"s mass, and are therefore attached to the plane"s center of mass. If the plane moves, the wheels move with equal momentum. If the wheels move, the plane moves with equal momentum. Yes, this is the same case with the car. No, the car"s wheels do not...

Negative. The forward momentum of anything on wheels is transfered to the wheels as angular momentum, regardless of where the push comes from. edit: Physicists learn about systems and motion using ideal systems, that is, systems with no friction and often times no mass to prove that universal...

When I manage to pull the paper with the same force with which I push the car, the car does not move.

No, I get that the wheels are not the source of the plane"s thrust. Source or not, if the plane accelerates, so do the wheels. Take a toy car, and push it. It is absolutely impossible that the conveyor belt would not hold the plane still if it matches the tangent acceleration. I"ve *just*...

...so the conveyor belt isn"t supposed to match the horizontal velocity of the plane? The landing gear is attached too, right? I think I followed y"all"s line of thought earlier, but I"m still going to take a look at the math now.

Okay, screw it. I"ll seek out some help from much more experienced physicists drawing up the free body diagrams for this, that way I can have it solved by sometime next weekend. Then, I"ll post the results. Time to knock out my Discreet homework and go to bed.

The problem with this model: Thus, when you pull the rope, the conveyor belt just goes faster, so that you don"t move. Thus, the escence of the question, phrased more simply, if this: Is enough vertical thrust supplied by the motion of the air due to the engines alone that a plane...

That"s what I got from both the question and the first posted explanation. The fact that the same folks who posted all that say that it moves (which makes perfect sense the way that they say it) is why I"ll be looking at the math. The problem with the idea that the plane does move forward...

That all clears up a good bit, thank you I think that I had missed the point of the car on the treadmill example before. Are there any planes that do operate by pulling air over the wings, such that they require no horizontal momentum for liftoff?

I think that in that case, forward momentum is an absolute must. Single prop planes work differently from dual props and jets in that they accelerate the entire body of the plane so that the plane moves relative to the air, instead of the air relative to the plane. Actually, those planes...

I hope that this thread has not scrolled too much after a couple weeks. I"d like to come back when I"m 100% on the answers to all of these questions. That is, with what I understand about physics thus far, I should have enough that I don"t need to rely on what a pilot once told me. I just...

I should agree here, but what I"ve been getting at is that the whole point of forward momentum should be moot, because it"s not the forward movement that supplies the lift. If breaks were ever devised that could handle the strain, a plane could sit still in one spot with the engines burning...

For the vertical acceleration Otherwise, the car on the treadmill would only model horizontal thrust Also, even if the plane does not move an inch horizontally until it takes off, it will take off. To demonstrate why the air is moving over the wings without the plane actually moving, place a...

The only way to understand this is through the simple acceptance of Newton"s Third Law, which can be proven pretty easily. When you set down an object on a table, gravity is pulling down on it, right? Well, why doesn"t it just pass straight through the table, and hit the ground? At the...

Aye, you"re right. I was just trying to think quickly of an example of vertical movement with no horizontal movement. The barrel really is a bad example.

If the string is attached to the top of the car, and not the front, yes.

It"s more like someone running on a barrel in water. They"re not moving horizontally because the barrel turns beneath them, but they are perpetually falling, thus the challenge in staying on the barrel. Thus, vertical motion with no horizontal motion. Then again, this analogy falls short when...

Summarily, yes, this is the case. I might suggest this as an exam question for whatever physics class ends up covering the dynamics brought about by potential differences in pressures. I"m pretty sure that advanced mechanics will cover this. This is an awesome thought experiment

It"s still relative to the ground, but not to the air. The big quote with the first scientific explanation was a little iffy on this point. It would be better to say that the air is not still with relation to the plane. What happens is you end up with static conditions for horizontal...

Rotational movement is subject to friction when said motion is surrounded by a surface in contact with another surface. If it were true that all rotational motion has no friction, then cars wouldn"t move. You"re confusing the motion of a pendulum with the motion of a wheel. Actually...

Adamantium molecules are packed extremely close together. As such, the surface of an adamantium conveyor belt is very, very smooth, and has a very, very low coefficient of friction. Thus, the question is... When your uncle"s plane slid off the conveyor belt in an uncontrolled manner, did he...

That one has more to do with the friction between the skateboard and the paper. Paper has a very low coefficient of friction, thus there was not enough grip on the wheels to match their movement. edit: He should try that again using a thick, coarse cloth. That"s a good observation, though...

It"s a fairly interesting experiment, to be honest. I"ve made conjectures based on Newton"s Laws, but the escence of physics lies in systems behaving differently than our intuition would lead us to expect. Since I don"t know enough about planes to sketch the math for this, or even a realistic...

The wheels don"t have to be powered, and no thrust needs to be directed toward them. Aye, there is no need to consider the plane"s chemical composition. The answer to this question lies in these three universal laws. The result would be the same with either a jet or prop plane. The engine...