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storysunfolding wrote:It would also depend on the material under the road. In some areas the roads are built on rock bed, in others it's over soft clay, sand/rock mix etc. So sometimes with the weather being really cold the clay contracts and pulls away from the road in spots. That makes a weak area where the concrete could crack.

The real question is if an airplane is on a runway that works like a conveyor belt where that belt perfectly matches the airplanes forward speed but in the opposite direction, does the plane take off?


Yeah- I went there. SOAP BOX RULES

Its forward speed over the conveyer or over the ground as a whole?

(Conveyer - no it has zero air speed, Ground - Yes it would have airspeed that provides the lift)

The conveyor would match it's speed over the conveyor. Thus if the plane was moving over the conveyor at 100mph, then the conveyor would be going 100 mph in the other direction.

I'd say it would still take off as the force that pushes the plane forward is independent of the ground. Well at least assuming that the bearings can take twice the speed needed for take off without creating enough friction to begin impeding forward movement in anything but a negligible way.

You have to generate lift. That is provided by the forward motion of the plane usually. If you had a 100 MPH wind blowing towards the airplane, and it is designated with ability to climb at that speed, it would lift without moving. You can do that in a wind tunnel with model planes. The key is the air moving over the top of the wing - it creates a lower pressure than the air going under the wing. The lower pressure lifts the wing up. So... a 100 mile an hour speed on an opposite running conveyor would do nothing to the planes lift unless it had adaquate wind speed over the wing.

Yep, the fact its touching the ground (or in this case a conveyor) is irrelevant, all thrust and lift are provided by movement of air - remember it has no drive through the wheels, its air being sucked through the engines and squirted out the back.


Otherwise, if it was dependant on the conveyor, it would fall out the sky as soon as lifting off

scan wrote:So... a 100 mile an hour speed on an opposite running conveyor would do nothing to the planes lift unless it had adaquate wind speed over the wing.

Exactly, since the plane's forward movement is independent of the ground (thrust pushing it forward as opposed to torque turning a wheel) the plane would still be moving forward at 100 mph, the conveyor would still be pushing back at 100 mph but the wheels would be turning at 200 mph

*Edit*- I was beaten!... anyway good thread derail everyone.


But why would you ask if a plane would crack the concrete? Suspicious what's been happening near your house?

storysunfolding wrote:

scan wrote:So... a 100 mile an hour speed on an opposite running conveyor would do nothing to the planes lift unless it had adaquate wind speed over the wing.

Exactly, since the plane's forward movement is independent of the ground (thrust pushing it forward as opposed to torque turning a wheel) the plane would still be moving forward at 100 mph, the conveyor would still be pushing back at 100 mph but the wheels would be turning at 200 mph

*Edit*- I was beaten!... anyway good thread derail everyone.


But why would you ask if a plane would crack the concrete? Suspicious what's been happening near your house?

Talking of derailing, would a locomotive derailing and running over a freeway crack the concrete?

First post edited.. some msitakes

Oh yeah, I'm just having an argument with another guy in my photoshop class.

He assures me that I am wrong and all highways in the US meets "national threat advisory" and at any moment the highways can be used for a transportation system for heavy war such as 200 tanks, and stuff.

I have no idea what he is talking about but does anybody know what he is talking about?

intotherain wrote:First post edited.. some msitakes

Oh yeah, I'm just having an argument with another guy in my photoshop class.

He assures me that I am wrong and all highways in the US meets "national threat advisory" and at any moment the highways can be used for a transportation system for heavy war such as 200 tanks, and stuff.

I have no idea what he is talking about but does anybody know what he is talking about?

The interstates can certainly be used for military purposes should the need arise, absolutely. It has nothing to do with the "national threat advisory" which is the color-coded system created by the DHS only a few years ago.

Read the History section on this one -

http://en.wikipedia.org/wiki/Interstate_Highway_System

Seems logical it would be designed to hold a lot of weight. DC-10, not sure.

If I read correctly in the past, the Autobahn could do it easily, but in the US we have been keeping the concrete much shallower than the Germans. They built the road very thick starting back in WW2, thanks to Hitler's plan to have a major transportation route for heavy equipment.

let me check with the local internet experts and get back to you.