OT Physics
Turbo Mini Forums

On 20th Jun, 2008 andygardner said:
So, can a plane on a runway sized treadmill designed to exactly match the speed of the wheels, moving in the opposite direction, take off?

Tim Rowe

"Is est totus perfectus per fumi quod speculum"

GTM Coupe Turbo

But it wouldn't take off.

pretty simple way to look at things would be:

Ground speed = 80mph

Air speed = 0mph

and the plane would not take off on the treadmill because on they work on the wind speed which would be the same as it is basically stood still. planes work on air speed.

I'll stick my 2p in now and say it would take off.

it wouldnt. take off. im sure i started a thread askign similar many years ago and it sparked a lovely mass debate.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

A plane that is stationary may well take off if there was an 80mph head wind. Dependant on the type of plane of course, im not talking 747 here.

if it's green and it stinks, it's botany.
if it wiggles, it's biology.
if it doesn't work, it's physics.

I learned this in engineering.

The plane wouldn't be stationary though. The fact it's on a treadmill is irrelevant because the thrust isn't a product of friction between the wheels and the surface, it's generated by the turbines which are throwing air out the back. Regardless of what the conveyor is doing the turbines will throw the same amount out the back and the plane will be propelled forward.

Granted the tyres will be spinning twice as fast and probably explode before it reaches the end of the runway though.

Bit of daft question really the one posed here just reminded me of the classic plane-treadmill problem.

Edited by andygardner on 20th Jun, 2008.

ahh i didnt realise you were talking about the plane also being opereated as normal. i thought you meant the pane sat on a runway which was running at take off speeds etc etc

Thrust causes the plane to move in the oposite direcion, causing air to move over the wings and generate lift. With a head wind on a stationary plane, air is moving over the wings and it too generates lift. The wheels do not move and the engines are doing nothing.

yes but in this instance lets take wind speed for 0mph form a stationary point.

would be funny to see a stationary plane take off in high winds

Are we still talking about the treadmill problem or the stationary plane in a headwind? lol

heres one for you. You are in a passenger train traveling at 120mph. You stand at the front of the carage and jump, will you land in tthe same place?

Oh and here is a real dangerous one. You are onn a boat at sea. The sea is rolling. You stand on the stern and when the boat is a tthe top of the wave, you jump as high as you can. what happens next?

is that jump off the train or just jup in the air?

what ends the stern?

if you just jump on a train and you are inside then you will land in the same place if the movement of the train is consistant. if you are outside then you will land further back than you started.

the boat i have no idea which end the stern is.

Ok then , let me expand a little on that. I should have said jump sttraight up.

There does that clear that up for you

And come on, you mean you don know which end of a boat is the stern?

The Bow is sthee pointy bitt and the stern is the blunt bit

im sticking with what i said above about you will land back on the train. and about the boat one then im going to say you will fall into the sea but have a longer fall than when you jumped. if the boat is moving that is hehe

in all honesty i dont know but im trying to think logically about it as to whether you in an open or closed environment (train)

I dont do boats me....lol

as madj says on a train you land where you started unless the train is acellerating/decelerating, or going up/ down an increadibly steep hill......

if you jump on the stearn i'd guess the boat will decend down the slope of the wave and you'll be left in the drink.

The train one, if you jumped straight up, relative to the ground (tracks) the difference would be about 45 meters?

The boat one, you'd hurt your legs? once you fall the height you jumped + the height the boat falls as it descends the wave.

I think :-

Edited by andygardner on 20th Jun, 2008.

Here's one. You have a helium filled balloon tied to your handbrake. You go round a left hand turn. Relative to the handbrake which way does the balloon move?

right because the handbrake is connected solidly to the car and so does not move with the force that is being applied to it as you go round the corner as the atmosphere in the car adapts the the conering. however the ballon can move as the string is not strong enough to overcome the force being applied to the ballon by the changing atmosphere during cornering.


now its my turn:
is it me or are we thinking way to hard about these things for a friday night?? lol

Does your car get lighter if you fill the tyres with helium?

yes becuase the air in your tyres is all part of the weight of your car and helium is lighter than air.

As you're thrown to the right the balloon goes left!

And yes, looks like we're the only sad acts not out on a friday night