Jump to content



Photo

MythBusters tackles "plane on a conveyor belt problem"


  • Please log in to reply
340 replies to this topic

#1 The_Decryptor

The_Decryptor

    STEAL THE DECLARATION OF INDEPENDENCE

  • 19,413 posts
  • Joined: 28-September 02
  • Location: Sol System
  • OS: iSymbian 9.2 SP24.8 Mars Bar

Posted 07 December 2006 - 00:28

Yes, it's that old conundrum, we had a lively discussion about it on the IRC, and i thought the forum would be a good place for a discussion on it (IRC doesn't exactly lend it's self to long lengthy discussions with multiple participants). Anyway, question is as such.

A plane (jet engine or propeller based) is sitting on a treadmill, the treadmill will always speed up to match the rotation of the wheel's, in reverse, no matter how fast the wheel's turn, the treadmill will match*.

Now, will the plane be able to take off?

* Ignoring such issues like the treadmill and wheel's spinning up to infinity, or the wheel's blowing or melting, or such.

(i know this has been discussed before, but i can't find the thread)



Update: The post about Mythbusters can be found here: http://www.neowin.ne...amp;p=589169105


#2 Caleo

Caleo

    Neowinian Senior

  • 1,827 posts
  • Joined: 30-June 04
  • Location: Michigan, USA

Posted 07 December 2006 - 00:30

Yes, the engines on the jet create the thrust, not the wheels... So, it'd overcome the treadmill & the wheels would probably explode doing so, but it would still take off.

#3 Jacky L.

Jacky L.

  • 12,058 posts
  • Joined: 27-October 04
  • Location: Hong Kong
  • OS: OS X Mavericks
  • Phone: iPhone 5s

Posted 07 December 2006 - 00:32

ah this question again, well i voted no, unless there is enough wind going through the wings from the thrust of the engine to be able to lift the plane....

the engine propels the wings through the air to create lift, but seeing the airplane is stationary, i dont see how the plane could fly

#4 davemania

davemania

    felo de se

  • 3,160 posts
  • Joined: 12-August 02
  • Location: syd.au

Posted 07 December 2006 - 00:32

Yes and pls don't bring back that thread :p

An analogy would be a model car on a treadmill with free axle being pulled by a string. If you pull the string, the car will move forward irregardless of the speed of the treadmill

#5 Caleo

Caleo

    Neowinian Senior

  • 1,827 posts
  • Joined: 30-June 04
  • Location: Michigan, USA

Posted 07 December 2006 - 00:35

Yes and pls don't bring back that thread :p

An analogy would be a model car on a treadmill with free axle being pulled by a string. If you pull the string, the car will move forward irregardless of the speed of the treadmill


And bingo was his name-o.

#6 Mr. Chronopoulos

Mr. Chronopoulos

    spook for hire

  • 2,475 posts
  • Joined: 23-December 04

Posted 07 December 2006 - 01:24

Decryptor, I explained this in great detail on IRC. Don't make me do it again. It will NOT take off. In fact, the plane will not move at all. Trust the third year physics student. Please.

#7 davemania

davemania

    felo de se

  • 3,160 posts
  • Joined: 12-August 02
  • Location: syd.au

Posted 07 December 2006 - 02:51

http://www.straightd...mns/060203.html
http://answers.yahoo...15213700AAaWyTK

the general consensus in other search results seems to indicate that it does. The plane doesn't remain stationary inregardless of the matching speed.

#8 vincent

vincent

    Neowinian Senior

  • 21,227 posts
  • Joined: 19-May 03
  • Location: W. Richland, WA

Posted 07 December 2006 - 02:53

**** here we go again :no:

#9 Rob2687

Rob2687

    ?

  • 13,333 posts
  • Joined: 27-April 03
  • Location: Ontario, Canada

Posted 07 December 2006 - 02:56

Just wait for them to do it on Mythbusters.

I say it does.

#10 Blues™

Blues™

    Level ?? Humanoid

  • 1,413 posts
  • Joined: 10-March 03

Posted 07 December 2006 - 02:58

the plane can only take off if there is sufficient lift
if there is no wind to get under the wings (ie the plane either isnt PHYSICALLY moving, or there isnt wind blowing) it will not take off

i hate to burst someones bubble but this is less of a physics question and more of an aeronautics question

#11 OP The_Decryptor

The_Decryptor

    STEAL THE DECLARATION OF INDEPENDENCE

  • 19,413 posts
  • Joined: 28-September 02
  • Location: Sol System
  • OS: iSymbian 9.2 SP24.8 Mars Bar

Posted 07 December 2006 - 03:33

If you think the plane isn't moving, explain why you think it isn't moving, it isn't tethered to the ground or anything.

#12 Jacky L.

Jacky L.

  • 12,058 posts
  • Joined: 27-October 04
  • Location: Hong Kong
  • OS: OS X Mavericks
  • Phone: iPhone 5s

Posted 07 December 2006 - 03:37

ok so i think i have both sides to the arguement, some may suggest that the plane does not fly, this is correct given the plane remains at stationary throughout acceleration. but keep in mind that the thrust of the plane will eventually reach a speed that it does not require forces induced from the treadmill, but actually the plane would accelerate such taht it is not in stationary (however the is the variable of air resistance), therefore the plane is NOT in stationary, it is accelerating forwards and need not the treadmill, and air would be moving through the wings and eventually propelling the plane to lift. i think thats the case, but i argued that if the plane in fact remains in stationary throughout the acceleration then it does not fly.

edit: ok nevermind the treadmill still matches the speed of the wheels, so that the plane will in fact remain at stationary all the time, think of it as friction less vaccume, wait, should we regard this as a friction less surface or vacume? that would be the absolute answer to the question...

edit: aite i got it, in the realistic case, it should be a friction less surface, therefore the engines would propell the plane forward and it may probably reach a speed with enough lift for flight. im out

#13 beh

beh

    Neowinian Senior

  • 1,658 posts
  • Joined: 22-December 03
  • Location: Central California

Posted 07 December 2006 - 04:53

The plane still moves because the plane is being pushed forward NOT by the wheels, but by the thrusters or propellers. The wheels just reduce friction between the plane and the ground. If the treadmill matches the speed of the wheels, then the plane will take off pretty much like normal except the wheels will be spinning twice as fast.

So the plane WILL take off.

#14 _sphinx_

_sphinx_

    Neowinian Senior

  • 4,093 posts
  • Joined: 05-June 05

Posted 07 December 2006 - 08:15

We've already been over this

Would it be efficient on aircraft carriers though?

#15 Echilon

Echilon

    GGTW

  • 10,414 posts
  • Joined: 18-May 03
  • Location: Chester, England

Posted 08 December 2006 - 15:58

Been asked before, and I'm still not convinced the plane would take off :p