Originally posted by: PurdueRy
Originally posted by: YOyoYOhowsDAjello
Originally posted by: JujuFish
Originally posted by: YOyoYOhowsDAjello
Originally posted by: BlinderBomber
Originally posted by: Rowboat
This is exactly my problem with the whole thing. The original myth involved a magic treadmill that could keep up with a semi frictionless wheel indefinitely which isn't going to happen.
Vote yes for mythbusters takeoff, the whole argument is based upon something that couldn't exist imo.
Please explain what you mean, the
original myth states that the treadmill is of indefinite length and that the speed is the same as the effective ground-speed of the plane. Outside of construction costs, it's plausible to build a runway that is a treadmill. What's impossible about that scenario?
There have been several "
original myths"
😛
The determination of the speed that the treadmill is trying to match is what causes a lot of these problems with needing infinitely accelerating treadmills and such.
For what it's worth, the original myth, as posed to ATOT by 911paramedic on February 10, 2006 (yes, you can all thank him for starting it all, here at least) is as follows:
Originally posted by: 911paramedic
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"
There have been different interpretations of what "plane speed" means
I think the term "plane speed" is fairly clear. I have never heard a pilot freak out in the middle of a flight because he saw that his wheel's rotational speed is zero. In fact, this just futher emphasizes how different a plane and car are. In a car wheel speed = speed of car(when converted to linear measurements). In a plane, they are not always related.
Plane speed refers to the speed of the plane, not the speed of the wheels.
Yeah, and when you think about what that means, then by the very definition of that speed control system, you must admit that the plane is moving relative to stationary objects for the treadmill to even be moving at all.
If we went to the popular example of what a car would do on the treadmill, that definition of speed of the car being relative to a fixed object doesn't make sense for the problem either. If the car is stationary relative to a fixed object, then the treadmill would not be moving. If the car is moving forward relative to a stationary object, then the treadmill starts to move to counteract it... but as soon as it was able to get up to that speed to counteract the car, the speed of the car relative to a stationary object would be 0 again, so by definition the treadmill's speed would be 0 again. Maybe I'm missing something, but having the speed of the treadmill be the same as the vehicle relative to an object but in the opposite direction doesn't make any sense.
If the treadmill is controlled by what the car's speedometer says, then it can keep it still though.
I don't know enough about planes to know all the ways of measuring its speed. I guess the airspeed indicator is the equivalent instrument to the car's speedometer, so you'd use that for the speed of the treadmill. The airspeed indicator would tell you the same speed as relative to a stationary object though in this case as opposed to what a car's speedometer tells you.
I agree that the plane's wheel speed doesn't make sense to use for the plane's speed, but that's how some people have interpreted the problem, thus turning it into a situation similar to the car problem, except now they need a hypothetical infinitely accelerating treadmill to try to get the plane to stand still.
Why am I writing all this out? I must be crazy.
