Author Topic: Treadmill redux (Read 1178 times)

Donzo · « **Reply #30 on:** December 20, 2007, 09:42:00 PM »

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Originally posted by Gunslinger
BUT THERE'S NO AIR FLOW OVER THE WINGS!!!!!!!

Why not?

john9001 · « **Reply #31 on:** December 20, 2007, 09:44:03 PM »

http://www.youtube.com/watch?v=OWDEYpqS0yw&feature=related

runway, we don need no steenkn runway.

Gunslinger · « **Reply #32 on:** December 20, 2007, 09:47:15 PM »

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Originally posted by AKIron
Lift? Where we're going we don't need lift.

nore treadmills....hell no wheels either!

Just thought of this.

It's the same concept of tail wind on take off. Increased tail wind on take off reduces lift and requires more speed to counter effect it.

Thus if you had an infinate amount of space to take off with and a tail wind that constantly matched the speed of the air craft it would never take off. It would continue to accelorate until the mechanical limitations of the AC are exceeded.

DONZO,

A treadmill that matched the speed of the wheels would not allow a plane to accelorate reletive to the position of the earth......thus no air flow over the wings The wheels could be spinning at 300mph but the airplane is going 0.

It's like having a bike or a car on a dyno. The aerodynamics of a car have no play in vehicle on a dyno because there is no air flow over it.

a y

Donzo · « **Reply #33 on:** December 20, 2007, 09:55:09 PM »

Quote

Originally posted by Gunslinger

DONZO,

A treadmill that matched the speed of the wheels would not allow a plane to accelorate reletive to the position of the earth......thus no air flow over the wings The wheels could be spinning at 300mph but the airplane is going 0.

It's like having a bike or a car on a dyno. The aerodynamics of a car have no play in vehicle on a dyno because there is no air flow over it.

a y

Try this:
With everything as already stated....hook a super strong steel cable to the nose of the plane. Attach the other end to a powerful winch. Now, will the winch pull the plane forward?

Gunslinger · « **Reply #34 on:** December 20, 2007, 09:59:59 PM »

Quote

Originally posted by Donzo
Try this:
With everything as already stated....hook a super strong steel cable to the nose of the plane. Attach the other end to a powerful winch. Now, will the winch pull the plane forward?

as the question is stated.....no

the pull of the wench would only be counteracted by the treadmill as it matches the speed of the wheel.

AKIron · « **Reply #35 on:** December 20, 2007, 10:02:55 PM »

I'm wondering if many civilizations haven't at some point puzzled over this scenario building both frictionless wheels and lightspeed treadmills to put the question to rest. It could explain the black holes that dot our universe?

Gunslinger · « **Reply #36 on:** December 20, 2007, 10:09:02 PM »

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Originally posted by AKIron
I'm wondering if many civilizations haven't at some point puzzled over this scenario building both frictionless wheels and lightspeed treadmills to put the question to rest. It could explain the black holes that dot our universe?

get rid of gravity all together and lift becomes irrelevent!;)

Donzo · « **Reply #37 on:** December 20, 2007, 10:13:02 PM »

Quote

Originally posted by Gunslinger
as the question is stated.....no

the pull of the wench would only be counteracted by the treadmill as it matches the speed of the wheel.

This is from the link Chairboy posted (http://www.straightdope.com/columns/060203.html):

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As you point out, one problem here is the wording of the question. Your version straightforwardly states that the conveyor moves backward at the same rate that the plane moves forward. If the plane's forward speed is 100 miles per hour, the conveyor rolls 100 MPH backward, and the wheels rotate at 200 MPH. Assuming you've got Indy-car-quality tires and wheel bearings, no problem. However, some versions put matters this way: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." This language leads to a paradox: If the plane moves forward at 5 MPH, then its wheels will do likewise, and the treadmill will go 5 MPH backward. But if the treadmill is going 5 MPH backward, then the wheels are really turning 10 MPH forward. But if the wheels are going 10 MPH forward . . . Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed. Nonsense. The question thus stated asks the impossible -- simply put, that A = A + 5 -- and so cannot be framed in this way. Everything clear now? Maybe not. But believe this: The plane takes off.

AKIron · « **Reply #38 on:** December 20, 2007, 10:24:20 PM »

Soon the foolish have persuaded themselves that the treadmill must operate at infinite speed. Nonsense. The question thus stated asks the impossible -- simply put, that A = A + 5 -- and so cannot be framed in this way. Everything clear now? Maybe not. But believe this: The plane takes off.

There is a fallacy herein. For the belt to match exactly the speed of the spinning wheel requires that the plane be stationary. If the plane is stationary there is no airlfow over the wings. The plane must move forward relative to the wind to takeoff. As the plane accelerates so does the wheel and therefore the belt.

Gunslinger · « **Reply #39 on:** December 20, 2007, 10:26:04 PM »

Quote

Originally posted by Donzo
This is from the link Chairboy posted (http://www.straightdope.com/columns/060203.html):

but the plane would never move forward reletive to the earth.

Chairboy · « **Reply #40 on:** December 20, 2007, 10:30:54 PM »

Why the heck wouldn't it move? You may be assuming that the wheels are motorized, but it's the prop that pulls it through the air.

AKIron · « **Reply #41 on:** December 20, 2007, 10:33:42 PM »

Having reread your excerpt Donzo I realized I misunderstood the point of that poster. Apparently they are saying that since it is impossible for a belt to keep up in the alternate understanding of the scenario it is therefore an incorrect interpretation of the problem given. If I'm reading that right then I say bullocks. Two interpretations lead to two different results. Because only one is practical does not negate the other or make the intrepreter responsible for a poorly defined problem.

vorticon · « **Reply #42 on:** December 20, 2007, 10:58:16 PM »

meh, i can push my brother forward off his bike rollers. those also do what the treadmill does in this question.

AKIron · « **Reply #43 on:** December 20, 2007, 11:00:30 PM »

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Originally posted by vorticon
meh, i can push my brother forward off his bike rollers. those also do what the treadmill does in this question.

Can your brother fly? I didn't think so.

JimmyZ · « **Reply #44 on:** December 21, 2007, 12:04:20 AM »

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If I run on a treadmill I sweat more.......because there isn't any airflow on my body. Again no air flow no lift.

To simulate a prop plane, mount a winch on the wall in front of the treadmill, engage it when you are at full speed. Or to simulate a jet, get yourself one of those James Bond '60s jet packs and aim the thrust straight back. No matter how fast that belts moving, you ain't staying stationary.

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meh, i can push my brother forward off his bike rollers. those also do what the treadmill does in this question.

All it takes is just one devious mother ****er to outthink the hive mind of humanity.