Andthen

Hve you seen the number of fat people over here?

Hobbess

you are living in Canada not America?

iaink

There is no difference. Are you a canadian by any chance? Only Canadians dont recognise the fact that Canada and the US are 90% interchangable.

Hell, since moving here Ive become one of the millions of fat canadians.

But Im probably wrong...have been about everything else this thread has touched on it seems

koogar

Actually Iain, it's taken me months to find something I can correct you on
I'm sure you'd find it much easier to return the favour.

Hobbess

Not a Canadian, but can see the difference and happy that I'm trying to pretend to be a relatively active (softball, curling, snowboarding, hockey) thinnish Canadian wannabe and not a [stereotyping]pudgier American[/stereotyping]

Recent trip to Florida highlighted the difference. Maybe it's just a West Coast thing, what with the mountains and stuff that keeps the pounds off.

Anyway back to the treadmill or lack of it, the point is that the space around in Canada means why would you get on a treadmill when you could go out for that run in the space?!?

Andthen

Neither as it happens, but I'm in Toronto right now.

iaink

So you havent been here long enough to realise that Florida is in fact Canadas 11th province/ territory...where Canadians go to die.

Half those fat 'mercans were probably Canadian.

Jingsamichty

Hi Bill_S,

This has really got me gripped!! I started with the assumption that the magic treadmill is frictionless, and acts only in reaction to the rotation of the plane's wheels. No consideration of inertia or friction losses.

Until gravity is overcome by lift, all the thrust forces are routed through the landing gear and the wheels. As the wheels attempt to rotate forward, the magic treadmill rotates backwards, resulting in zero forward movement. As thrust increases, the wheels and treadmill accelerate up to ludicrous speads, way more than take off speed, but still, there should be no forward motion. Gravity ensures that the thrust forces go through the wheel/treadmill. As long as the treadmill reacts instantaneously with the rotating moments of the wheels, there cannot be forward motion.

The original poster stated that the the conveyor is "designed to match the speed of the plane exactly". On that assumption alone, surely the plane cannot move?

This is fun - just like Johnny Ball's science programmes!

iaink

Ah, but they arent, the thrust acts on the airframe, pushing it along horizontally, relative to the air. Whether the wheels move or not is neither here or there, the wheels are free to rotate independent of the air frame (the brakes are off), and the plane is moving relative to the air, which is all that matters. What the treadmill is doing is of no consequence once the initial friction of the wheel bearings is overcome and the wheels start to rotate.



Nope, as the treadmill moves, it just spins the wheels on the plane faster, so baring a catastrophic wheel bearing failure and the sudden application of a whole lot of friction, the thrust from the engines keeps pushing the airframe forward anyway, relative to the static air, eventually creating lift.



except they dont, as the force of the engine is pushing on the airframe, and the wheels are rotating entirely independently of that So the plane is going forward at 200mph, the treadmill is going backward at 200mph. The wheels are turning at 400mph....but the plane is still being pushed forward into the air by the engines thrust at 200mph, so it will take off

It is rather. Sadly its the most I have used my brain today.

As you can see I have jumped ship here and am now in the it'll take off crowd.

Surrey Expat

At this point fire trucks might be a useful consideration.

steve666

Not a single one of you has put your finger on the one obvious thing staring at you for the whole 5 or whatever pages!

iaink

What idiot wrote that!

You know they let anyone post any old crap here dont they.

steve666

Don't be so hard on yourself.

iaink

The first and second comments were not necessarily related you know

Jingsamichty

I think this is the key to the riddle. I got fixed on the treadmill negating the speed of the wheels. It's a semantic puzzle rather than a physics puzzle... if the planesis going at 100mph, the treadmill is going at -100mph. The wheels are going at 200mph.... but nonetheless the plane is going at 100mph. If the plane is moving it can take off.