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Seriously now, can it take off or not? What do you think?
12-12-2005, 01:12 PM
#78
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RE: Seriously now, can it take off or not? What do you think?
In order to move the plane forward they must turn faster than the object they are pushing against, which is usually the ground. Is this the case?
12-12-2005, 01:17 PM
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RE: Seriously now, can it take off or not? What do you think?
the object they are pushing against
12-12-2005, 01:20 PM
#80
RE: Seriously now, can it take off or not? What do you think?
ORIGINAL: w_benjamin
The reality is you'll break something on the plane before you get it to fly.
The reality is you'll break something on the plane before you get it to fly.
You are wrong - The belt will break before the plane will
Now that sentence is just as ridiculous as yours is.
You keep talking about a HYPOTHETICAL Belt vs. a real airplane.
Ok, let's try this:
Q: If you tie an imaginary rope to the tail and anchor it to a fence post will the plane fly?
A: YES - BECAUSE THERE IS NO SUCH THING AS AN IMAGINARY ROPE!!!
Abraham Lincoln once asked "If you count a dog's tail as a leg, how many legs does a dog have?
Answer: Four - counting a tail as a leg doesn't make it a leg.
Once again: REAL airplane / REAL belt - The faster the belt moves, the less kinetic friction developes between the wheels and the belt, so the wheels will slide along the belt as if it were made of ice. As the belt moves faster to compensate, the LESS Friction it developes.
If you disagree, you might as well tie the plane down to the belt with your imaginary rope.
ORIGINAL: w_benjamin
The reality is you'll break something on the plane before you get it to fly.
The reality is you'll break something on the plane before you get it to fly.
12-12-2005, 01:21 PM
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RE: Seriously now, can it take off or not? What do you think?
Poorly worded, I concede. The prop is generating the energy used to turn the wheels and move the plane forward. Back to the question: Are the wheels turning faster than the object they are resting on?
12-12-2005, 01:22 PM
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RE: Seriously now, can it take off or not? What do you think?
ok truly last post on this.
Whatever you think friend.
You bet, sure it can't fly..but be careful, monkeys are going to be leaving you're derrier in rapid fashion.
And to answer your question, no, they don't have to. Because the wheels are simply spinning, not creating the turning force. The prop is doing that. This little point is what has you and everyone that thinks the plane won't fly confused...which me, Dick and a host of others has tried to outline over the course of several days.
I am truly sorry it won't compute, but I have done my best do show why the plane can fly given the problem.
Good luck with you're stationary planes.
Whatever you think friend.
You bet, sure it can't fly..but be careful, monkeys are going to be leaving you're derrier in rapid fashion.
And to answer your question, no, they don't have to. Because the wheels are simply spinning, not creating the turning force. The prop is doing that. This little point is what has you and everyone that thinks the plane won't fly confused...which me, Dick and a host of others has tried to outline over the course of several days.
I am truly sorry it won't compute, but I have done my best do show why the plane can fly given the problem.
Good luck with you're stationary planes.
12-12-2005, 01:30 PM
#84
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RE: Seriously now, can it take off or not? What do you think?
"When two surfaces are moving with respect to one another, the frictional resistance is almost constant over a wide range of low speeds, and in the standard model of friction the frictional force is described by the relationship below. The coefficient is typically less than the coefficient of static friction, reflecting the common experience that it is easier to keep something in motion across a horizontal surface than to start it in motion from rest. " - http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html
12-12-2005, 01:38 PM
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RE: Seriously now, can it take off or not? What do you think?
if the wheels are in contact with the ground, then the opposing objects movement is stationary and the net value of the rotation of the wheel is that the connected object(the plane) moves forward the distance of the circumference. If the opposing object objects movement is counter to the rotation of the wheel at a ratio of 1:1 then the net value of the rotation in regards to moving the object forward is 0.
12-12-2005, 01:38 PM
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RE: Seriously now, can it take off or not? What do you think?
quote:
So Philip, do you think if the conveyor matched the WHEEL speed that the plane could take off?
So Philip, do you think if the conveyor matched the WHEEL speed that the plane could take off?
But if the conveyor matches the forward speed of the plane/wheels relative to the still ground that the conveyor is sitting on, only in reverse, that's a plausible situation. (Wouldn't be perfectly immediately matching, but could be instantaneous within milliseconds with electronic speed control). I think this question was originally designed to flush out those who can't grasp the concept that a plane is propelled through the air, and the wheels and contact with the ground have little to do with it. Notice I didn't say "nothing" to do with it. I think the reverse motion of the conveyor could slow the accelleration and lengthen the take-off run, but not keep the plane from flying.
... The plane will be moving forward through the air. Because, the plane is pulled through the air by its prop (or jet). Running the conveyor under the wheels simply turns the wheels faster (or slower). But unless the plane has brakes that are on, that won't matter very much. The plane moves through the air, down the conveyor, and lifts off into the wild blue.]
Edit: Adding a little more
I completely agree with Craig's post.
And, perhaps it will help some to think of it this way: You're a little kid with a toy plane in your hand. You provide the thrust to make it move forward (and the lift to make it fly, but that's beside the point for this discussion). You roll your little plane along a table top. It's not too hard to get it up to flying speed, right? Now roll it along a conveyor belt moving backwards at flying speed. It's still not very hard to move the plane up to flying speed, as long as you don't press down too hard, is it? But man, those wheels are spinning fast. Cool!
12-12-2005, 01:50 PM
#87
RE: Seriously now, can it take off or not? What do you think?
The prop pulling the plane forward -does NOT turn the wheels!!!!!!!!!!!!!!
The wheels simply turn to reduce friction between them and the ground/belt pasture /runway.
Because--it is easier to do than slide along.
If you try to pull a stubborn dog - -and she starts to move her legs -the friction is reduced -and she moves- but YOU are not moving her legs. That is just her reaction to pulling .
I asked Libby about this and she is still wondering why anyone has not yet figured this out.
The wheels simply turn to reduce friction between them and the ground/belt pasture /runway.
Because--it is easier to do than slide along.
If you try to pull a stubborn dog - -and she starts to move her legs -the friction is reduced -and she moves- but YOU are not moving her legs. That is just her reaction to pulling .
I asked Libby about this and she is still wondering why anyone has not yet figured this out.
12-12-2005, 01:52 PM
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RE: Seriously now, can it take off or not? What do you think?
"You roll your little plane along a table top. It's not too hard to get it up to flying speed, right? Now roll it along a conveyor belt moving backwards at flying speed. It's still not very hard to move the plane up to flying speed, as long as you don't press down too hard, is it? But man, those wheels are spinning fast. Cool! " Your flaw is that your setting the speed of the conveyor to your flying speed.., not the speed of the wheels.
12-12-2005, 02:00 PM
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RE: Seriously now, can it take off or not? What do you think?
Your flaw is that your setting the speed of the conveyor to your flying speed.., not the speed of the wheels.
12-12-2005, 02:06 PM
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RE: Seriously now, can it take off or not? What do you think?
The fact is that kenetic friction is a constant(albiet with a lower coefficient than static). You need to provide enough energy to the wheels to overcome the resistance the ground provides in order to move the plane forward. If it's on a conveyor, you need to provide that energy plus the energy being acted on the plane from the conveyor. Remember, according to the question, the wheels CANNOT be going at a faster speed than the conveyor, so as you provide more energy to the wheels, the conveyor matches it with the same amount of energy.
12-12-2005, 02:11 PM
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RE: Seriously now, can it take off or not? What do you think?
The question is not flawed. I will repeat it if you can't remember it. The speed of the conveyor is dependent on the speed of the wheel. Believe it or not, the speed of the wheel is dependent on the amount of thrust being generated by the plane. If the thrust goes down, the speed of the wheels and respectively the conveyor goes down until it is standing at rest. If the thrust goes up, the speed goes up until it is at peak thrust. In either case, the plane did not move.
12-12-2005, 02:18 PM
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RE: Seriously now, can it take off or not? What do you think?
In your interpretation of the question, when you spin up the prop, and the plane begins to move, what happens? Please give me a series of events.
12-12-2005, 02:23 PM
#93
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RE: Seriously now, can it take off or not? What do you think?
As soon as the plane begins to move, the instant, the conveyor matches the speed of the wheels exactly, forcing it backwards at the same rate it is trying to go forward.
12-12-2005, 02:29 PM
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RE: Seriously now, can it take off or not? What do you think?
Because it is not an action, it is a reaction. Remember, the conveyor is dependent on the speed of the wheel, not the other way around.
12-12-2005, 02:31 PM
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RE: Seriously now, can it take off or not? What do you think?
Because it is not an action, it is a reaction. Remember, the conveyor is dependent on the speed of the wheel, not the other way around.
12-12-2005, 02:35 PM
#97
RE: Seriously now, can it take off or not? What do you think?
Ok, you're holding a broomstick so it is straight up and down.
Why doesn't the broomstick fall out of your grasp? Friction.
Remove the friction, and the broomstick falls - Right?
So the faster the magic belt moves, the less friction it generates.
Since the plane is being pulled by the prop, and there is minimal friction between the wheels and the belt, it is physically impossible for the belt to generate enough friction to hold the wheels back.
Why doesn't the broomstick fall out of your grasp? Friction.
Remove the friction, and the broomstick falls - Right?
So the faster the magic belt moves, the less friction it generates.
Since the plane is being pulled by the prop, and there is minimal friction between the wheels and the belt, it is physically impossible for the belt to generate enough friction to hold the wheels back.
12-12-2005, 02:43 PM
#98
RE: Seriously now, can it take off or not? What do you think?
How fast will 5" free turning wheels turn to counter 26lbs of thrust from a propellor driven craft??
From what I gather this is what you are saying will happen.
The conveyor will match (in speed) the amount of thrust produced by a turning prop.
Thats like saying a strong enough wind can overcome the horsepower of Indy 500 car. (i.e. blow the car to a stand still while it is driving full speed.)
Neither of these senarios is capable of being produced. The amount of energy needed by one to cancel out the other is to high.
From what I gather this is what you are saying will happen.
The conveyor will match (in speed) the amount of thrust produced by a turning prop.
Thats like saying a strong enough wind can overcome the horsepower of Indy 500 car. (i.e. blow the car to a stand still while it is driving full speed.)
Neither of these senarios is capable of being produced. The amount of energy needed by one to cancel out the other is to high.
12-12-2005, 02:46 PM
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RE: Seriously now, can it take off or not? What do you think?
Picture two cars pushing against each other. The first car wants to push the other backwards. The second car only want to keep the first from moving forwards. As the first car begins to push, the second car matches him. But as he lets off the throttle, the second car does likewise. In other words, the second car only throttles up when the first car does..., it does not initiate the throttle up. In this instance, the first car does the 'acting', and the second car does the 'reacting'. If the first car was not there, the second car would do nothing.
12-12-2005, 02:49 PM
#100
RE: Seriously now, can it take off or not? What do you think?
Now put one car on wheels made of ice and what happens?
The prop is pulling through air which provides propulsion.
The wheels are moving so fast that there is no friction on the belt.
YOU TELL ME WHAT WILL HAPPEN
The prop is pulling through air which provides propulsion.
The wheels are moving so fast that there is no friction on the belt.
YOU TELL ME WHAT WILL HAPPEN