Monday, May 14, 2007

Here's a question for you

So there is a plane on a runway. The runway is a treadmill that will move in the opposite direction of the airplane, and at the same speed in the opposite direction as the airplane (so if the plane moves 5mph forward, the treadmill moves 5mph in the other direction, etc). Will the plane take off?

Just so you know, this question gets posted about every 3 months on offtopic.com and it blows up into a 100 page thread with lots of swearing and arguing. There are some seriously smart people on there (pilots, engineers, etc) and it is a dead 50/50 split. My roommate is absolutely convinced it will take off because the engines are applying force to the air not to the ground like a car, so it doesn't matter how fast the wheels are spinning in place, it will take off. I say it won't because without the plane physically moving foward, there is no lift. So will it?



edit: I think we need G-reg in here to get the pilot's perspective.

edit2: Here is what a physics professor from Rutgers says about it:

The only thing that matters is the motion of the wings through the
air. This is what develops lift. The force pulling the plane
forward is developed by the propeller's motion in the air and has
little to do with the wheels or the runway. Since the plane still
moves forward (due to the force of the propeller against the air) it
will still accelerate to the speed required for takeoff. When it
leaves the ground the wheels will not be rotating but otherwise it
will be a perfectly normal takeoff.

12 comments:

Sara said...

No, there is an elephant in the way.

(see Feb. 15th post)

Trent said...

Without the wind going around the wings there is no way the plane will lift... UNless being pulled by the Monorail Cat!

Brian said...

I think there's only one way to figure this one out...

Chris said...

I agree with Trent. The basic physics of air flight show that there needs to be a vertical push from the force of the air travelling around the wings (this is called friction). Your room mate has a point, but even though the engines are pushing, there is no lift being created on the plane. It is running full steam ahead and going no where very fast.

It is possible that Speed Racer & Mach 5 could help the plane take off, but without them it is dead in the water.

Justin Fox said...

I agree that Monorail Cat would probably need to be involved. Something to consider is the fact that the wheels on a plane move absolutely independently of its forward "drive" mechanism. I still don't think the bastard takes off personally. Just google "will the plane take off?" and you'll see some interesting theories (including a 519 page thread on a physics forum here:http://forum.physorg.com/index.php?showtopic=2417&st=0)

squez said...

I would also have to argue that because there is no forward motion there could be no way that the plane could get any sort of lift inevitably leaving it going at high speeds on a treadmill. Though I would also say that if monorail cat was involved in some way the plane would be flyin in no time.

Sara said...

My bro, an engineer, says this:

"No way. A plane takes off because of lift generated from air moving over
the wings. In this case, the plane and the air remain stationary, therefore
no lift."

Brian said...

I don't even think that Monorail Cat could help that plane get off the ground.

Fox, I just noticed the Play Nintendo Online link that you have posted. That page rules. I could get fired because of that link...
;)

G-reg said...

No. Don't even see the argument. No airspeed = no flying.

Justin Fox said...

I think Mythbusters needs to be involved, but apparently they won't do it or something.

G-reg said...

Ok, if it's a treadmill the size size/length of a runway it will take off when it gets to a certain airspeed the wheels will just be spinning faster. Still not much up for debate.

Shelly said...

plane can't fly without lift. No argument.