Author Topic: plane on a conveyor belt? (Read 26349 times)

eskimo2 · « **Reply #540 on:** January 29, 2007, 04:57:00 PM »

Quote

Originally posted by takeda
No conceivable arrangement that can only spin the wheels can keep the plane from gaining forward airspeed once thrust is applied.
If the threadmill is spinning the wheels with 30g of acceleration, once those engines start pushing, the wheels have no other option but accelerate at say 32g.

I can't really follow your diagram that well, I feel that a few arrows and labels are missing, but you can't oppose the force exerted by the threadmill and plane on the wheel, because they are in fact working in the same direction, making the wheel spin forward.
The only way to stop the plane using the wheels is countering that spin, ie. brakes or blocks. A threadmill running opposite will just spin them faster and the plane will fly, a threadmill running in the same direction means the plane will fly, because it would be more aptly called a catapult.

Takeda,

Read and watch the movie:

Here is a paper treadmill; the source off acceleration is a falling shoe tied to the paper. On the paper treadmill are a mouse ball, a copper pipe with a rubber band glued around it for traction, and an acrylic ball that may have skid/slip some.

Picture of the set up:

AVI:
http://hallbuzz.com/movies/paper_treadmill.AVI

QuickTime
http://hallbuzz.com/movies/paper_treadmill.MOV [/B][/QUOTE]

takeda · « **Reply #541 on:** January 29, 2007, 05:10:18 PM »

You forgot to have the other shoe pull your objects forward. Planes tend to have engines that make them go forward.

2bighorn · « **Reply #542 on:** January 29, 2007, 05:16:01 PM »

Quote

Originally posted by eskimo2
2bighorn, when you drop things on your planet, which way do they fall?

No offense Eskimo, but for a teacher your reasoning is very weak. True, my drawing is extremely simplified, but follows the logic of directional change of an applied force over a circular body. I didn't want to spend time on geometric derivation just to prove something to you what you are not capable of understanding.

hitech · « **Reply #543 on:** January 29, 2007, 05:24:09 PM »

Quote

In order for force B to cancel force C, force B must work on the axis of rotation.

Bighorn this is not true, wish I had a physics book around to sight the theorem.

But it states that you can convert any (force vector at a point) to the same force vector at the CG of an object along with a torque.

Basicly a force is a force is a force no mater where you exert it on an object.

The only thing that changes when you push on a different spot is you add a torque.

Do some google searching you will find the theorem.

HiTech

eskimo2 · « **Reply #544 on:** January 29, 2007, 05:27:16 PM »

Quote

Originally posted by takeda
You forgot to have the other shoe pull your objects forward. Planes tend to have engines that make them go forward.

What’s stronger, a bear or some ants?

JB88 · « **Reply #545 on:** January 29, 2007, 05:28:50 PM »

Quote

Originally posted by eskimo2
What’s stronger, a bear or some ants?

a. how many ants?
b. what is being acted upon by the subjects?

eskimo2 · « **Reply #546 on:** January 29, 2007, 05:46:27 PM »

Quote

Originally posted by 2bighorn
No offense Eskimo, but for a teacher your reasoning is very weak. True, my drawing is extremely simplified, but follows the logic of directional change of an applied force over a circular body. I didn't want to spend time on geometric derivation just to prove something to you what you are not capable of understanding.

You need to do some experiments and test your theories; you have some ideas that are exactly opposite of how things work. Pick up your bicycle, point it backwards down your driveway, crank the pedals so the wheel spins, jog down the driveway and set the wheel down. Note which way the rotational inertia of the spinning wheel kicks the bike. Now try it the other way. Even better, if you have a belt sander, set the spinning wheel down on the sander.

2bighorn · « **Reply #547 on:** January 29, 2007, 05:55:33 PM »

Quote

Originally posted by hitech
Basicly a force is a force is a force no mater where you exert it on an object.

Not true, force has a magnitude and direction. In case where more than one force is acting upon object, depended on the direction of forces, net sum can be of different magnitude and/or direction.

eskimo2 · « **Reply #548 on:** January 29, 2007, 06:14:03 PM »

Quote

Originally posted by JB88
a. how many ants?
b. what is being acted upon by the subjects?

How many ants is the correct answer! Just because a force seems small does not mean that it is limited to always being small.

You saw the cylinder/ring accelerate to the left in the movie. Now imagine that it has 999 times its mass (representing the mass of the plane) sitting on it (through an axel). The entire thing will only accelerate at 1/1000 it current acceleration now, right? That seems like nearly nothing, and it almost is. Now imagine the treadmill accelerating at 1000 G’s. Now the thing will accelerate to the left at the same rate as the cylinder in the movie. See how a force that we typically dismiss can be great?

A plane that could take off with its wheels locked may also be able be able to take off on the super treadmill.

The tire/wheel flywheel will hold as much force through the rotating contact patch of its tire to the treadmill as a plane with its wheels locked and engine on full power does through its stationary contact patch of its tire and the runway. Most planes can not take off with their wheels locked and also would not be able to take off on the super treadmill.

2bighorn · « **Reply #549 on:** January 29, 2007, 06:53:06 PM »

Quote

Originally posted by hitech
But it states that you can convert any (force vector at a point) to the same force vector at the CG of an object along with a torque.

We are dealing with rotational motion here, it is important if force passes through the center of mass or not. Conveyor's vector force is translated into rotation or to be more exact we get 'translational rotation' (since it does not pass the center of mass). Once we have rotation we have angular momentum as well.
To simplify definition of the angular momentum it is measure of the difficulty of bringing a rotating object to rest.

In case to understand the logic of opposing forces translated into rotational motion, lets say that two equal opposite forces acting on the circular object from an equal distance apart can make the object to rotate (instead of canceling each other out).

Therefore your statement of canceling forces would be true as long as we're not dealing with rotational motion.

eskimo2 · « **Reply #550 on:** January 29, 2007, 06:57:43 PM »

2bighorn,

Seriously, I’d love to read your explanation of how these thing work:

[/B][/QUOTE]

JCLerch · « **Reply #551 on:** January 29, 2007, 07:02:35 PM »

There is a problem with the super tread mill theory. For the airplane under power to not move forward with respect to the ground that the tread mill is attached to, the tread mill must accelerate at "The HiTech Number" (910 feet per second per second).

The tread mill must continually accelerate at this rate for as long as the airplane engine is producing thrust. If we supply the airplane with an externally attached fuel supply, it will only need to run for a relatively short period of time before enough energy has been stored in the system for gravitational time dilation to become something that must be considered.

If we don't consider the effects of relativistic motion in this system, in just over 2 years the linear speed of the tread mill belt will exceed the local speed of light. I'm pretty certain this will pose a problem.

2bighorn · « **Reply #552 on:** January 29, 2007, 07:06:47 PM »

Quote

Originally posted by eskimo2
The tire/wheel flywheel will hold as much force through the rotating contact patch of its tire to the treadmill as a plane with its wheels locked and engine on full power does through its stationary contact patch of its tire and the runway. Most planes can not take off with their wheels locked and also would not be able to take off on the super treadmill.

I believe somebody already told you that your analogies don't hold the scrutiny of reasoning.

Would you please explain in what way does the conveyor brakes the airplane's wheels? And please, no more movies of belt sander and flying shoes. Just words if possible.

2bighorn · « **Reply #553 on:** January 29, 2007, 07:10:33 PM »

Quote

Originally posted by eskimo2
2bighorn,
Seriously, I’d love to read your explanation of how these thing work:

Seriously, after running those toys forward and flywheel has enough energy stored and you put them back on the ground, will they suddenly move backwards?

eskimo2 · « **Reply #554 on:** January 29, 2007, 07:17:14 PM »

Quote

Originally posted by JCLerch
There is a problem with the super tread mill theory. For the airplane under power to not move forward with respect to the ground that the tread mill is attached to, the tread mill must accelerate at "The HiTech Number" (910 feet per second per second).

The tread mill must continually accelerate at this rate for as long as the airplane engine is producing thrust. If we supply the airplane with an externally attached fuel supply, it will only need to run for a relatively short period of time before enough energy has been stored in the system for gravitational time dilation to become something that must be considered.

If we don't consider the effects of relativistic motion in this system, in just over 2 years the linear speed of the tread mill belt will exceed the local speed of light. I'm pretty certain this will pose a problem.

Thank you! It’s refreshing for this thread to leap forward with ideas. Are you saying that the treadmill gains so much mass as it nears light speed that it will screw up time?