Riddle me this... riddle me that....

[Admin]

If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?

[daddywags]

What walks on four legs in the morning...two in the afternoon...and three in the evening?

[KillSwitchEngage]

^^^

a human

crawls
walks
uses a cane
;)

[KillSwitchEngage]

If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?

When an airplane takes off, there is one major forward force… the forward thrust. The main rearward force is air resistance. The turning of the wheels provides a small frictional force, but because the wheels are free-rolling, this friction is very small. Unless the wheels are locked, the friction is always going to be less than the thrust, which means that the overall force is still forward, and the plane WILL STILL MOVE!!:eek:

[Kelly087]

Yeah, I would have about the same response, if it was a car it'd be a totally different situation.

[modogg85]

easier terms, the thrust needed to make the play go 100 knots is greater than 100 knots.

[Kelly087]

I don't think there'd be much force against the plane from the wheel resistance against the conveyor belt. So force needed to push the plane forward at 100 knots on a normal runway wouldn't be much different than it would with the conveyor belt.

[D1STURB3D]

If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?


the plane has to have lift, so the plane will just stay in the same spot and not take off

[Kelly087]

the plane has to have lift, so the plane will just stay in the same spot and not take off

Why would the plane stay in the same spot?

[D1STURB3D]

the plane is going 100knots forward and the conveyer belt is going 100knots backwards = 0knots

it cant fly at all

[D1STURB3D]

never mind if it says it need to make enough thrust to go 100knots so in reality it is going 200knots it doesnt say it IS going 100knots. had to read it like 5 times

[Kelly087]

The plane's speed is irrelevant to the ground. The plane makes its thrust from air. It's how their engine works. The wheels barely generate any friction with the ground so it's still able to take off.

[Admin]

the plane is going 100knots forward and the conveyer belt is going 100knots backwards = 0knots

it cant fly at all


Haha.. think about it some more... it DOES take off.

[D1STURB3D]

i know right after i put that i put another post, can you add a delete you own post or something to the forum

[bigces]

If an airplane is on a large conveyor belt and is trying to take off by exerting the thrust needed to move it forward at 100 knots, and the conveyor belt starts moving backwards at 100 knots, will the plane be able to take off, or will it just sit stationary relative to the ground, with the backwards speed of the conveyor belt counteracting the forward thrust of the plane?

:420what:

[Kelly087]

I read another variation where the conveyor belt moved against the plane with the same speed as the plane was moving, so if the plane was starting to move forward the conveyor belt would "stop" the plane from moving, which obviously it doesn't.

[Kelly087]

Sooooo.... if you watch Mythbusters I hear they're gonna be testing this out. I'm gonna record it if I can and watch it. Should be interesting.

[skogey10]

You all must be Engineers and Physicists to overthink it that much.

[Kelly087]

Ha, yeah.... I am. Civil Engineering.

[skogey10]

Civil? Well that's just pretending to be an engineer, you should get this :O

[Kelly087]

Haha, yeah... well it's one path towards Acoustical engineering. A different kind of physics than that problem, but we still cover it all.