Physics Problem

[Black2003SS]

http://www.clubgp.com/newforum/tm.asp?m=34...tmode=1&smode=1

 

 

A plane is standing on a runway that can move (like a giant conveyor belt). This conveyor has a control system that tracks the plane's speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

 

Will the plane be able to take off?

 

Pretty interesting topic. You can see how it would be confusing to the average person. The plane would obviously take off.

[misterp]

Yeah we already had that one. All of us got it wrong except Big O

 

Mr. P.

[Black2003SS]

Grrrr....sorry.

[misterp]

It's a good topic, that problem just pisses me off cause I reasoned wrong.

[SS--BLOWN]

I changed my answer. See page 12 of the clubGP forum discussion. I logged in as Mdog.

Edited December 14, 2006 by SS--BLOWN (see edit history)

[wody]

Didn't see this post before--and don't want to start another debate--but the plane will not take off.  If it sits in place on the belt, then no air is moving across the wings.  No air = no lift = stationary plane.

<{POST_SNAPBACK}>

i agree but until someone tries it everyone is going to argue about it.

 

Alan

[Black2003SS]

I found the answer online, it will take off. I lost the link though...searching for it.

[Oo p0op oO]

it will take off.....we have one in our back yard this is how my dad gets his bombers in the air......he has his own army...........DUH

[brobradh77]

I am going to reason with it and say no. The plane is acting as if on a treadmill. Yes it can reach the speeds needed for take off but the resistance from the air needed for the wings to lift the plane off the ground is non existance due to the plane is just idiling in one spot. Thats my .02

Edited December 13, 2006 by brobradh77 (see edit history)

[TexaSS]

I remember seeing this before. The answer was something like the plane will take off because it has something to do with lift and thrust, blah, blah and the wheels don't really matter.

[Big O]

Yeah we already had that one.  All of us got it wrong except Big O   

 

Mr. P.

<{POST_SNAPBACK}>

 

 

lol ... I'm touched that you remembered ... man reading this topic gets me all worked up again ...

 

If i remember right it was several pages long on theories ... it was a good read.

[AJSmyth]

it will take off.....we have one in our back yard this is how my dad gets his bombers in the air......he has his own army...........DUH

<{POST_SNAPBACK}>

 

 

[PladdPezzPunk]

simple physics if you went to school for engeneering air speed and ground speed are two different things. wheels will spin twice as fast though. hint for any one thinking about it, the earth is rotating like a conveyor belt.

 

now the real kicker, if your in a giant wind tunnel and their is a tail wind exactly equal to the planes forward velocity, will the plane take off?

[misterp]

I remember seeing this before.  The answer was something like the plane will take off because it has something to do with lift and thrust, blah, blah and the wheels don't really matter.

It's a trick question and impossible situation - the answer is that there is no way possible to make a plane stay stationary on a treadmill; unless it is tethered it will pull itself off the treadmill, down the runway, and into the sky because the prop (or jet) is acting on the AIR (not the ground) to move itself. To make a plane stay stationary you must employ an 'air treadmill' rather than a 'ground treadmill', ie put it backwards in a wind tunnel.

 

Mr. P.

 

MORE: If it were a CAR with wings, it wouldn't fly because the car is putting power into the ground which the treadmill can counteract; an airplane puts power into the AIR.

Edited December 14, 2006 by misterp (see edit history)

[Black2003SS]

Best way to describe it is with an experiment you can do yourself on a tredmill.

 

 

Ok...You have a toy plane with wheels and tredmill. Place the plane on the tredmill. Now, since the "toy" plane does not have real engines, we will use your finger as the propulsion. Ok? Now, using you rfinger you begin to push the plane up the tredmill belt (upstream). Let's say you push it at 3mph relative to a fixed point off of the tredmill. Now, the tredmill recognizes that the toy plane is moving at 3mph. The tredmill turns its belt at 3mph in the opposite direction correct? Now you still have your finger on the plane ok? So you are still applying force to the plane to keep it moving at 3mph in the direction you were pushing it right? If you take your finger off, the toy will slow and eventually start going the other direction with the tredmill. BUT you are still pushing at 3mph relative the FIXED point on the tredmill...All you simply have to do is push the toy plane to the speed it requires to provide lift. You can continue to turn up the tredmill, but all it will do is make the wheels spin faster, it will not counter the force you are providing by your finger. The force of the propulsion is provided by your finger, not the tredmill. They are completely independent of each other.