Mintman – what about when they are outside of the earth's atmosphere – how do they accelerate then?

The rocket itself is 'pushing' against the inertia of the propellent which is being ejected.

I've had mornings after a vindaloo like that.

FFS, THE GROUND SPEED IS TOTALLY IRELAVANT!

A plane will only fly given sufficient AIRSPEED.

I agree, but surely the airspeed is zero? The treadmill is going round, the wheels are moving but the plane is staying still, no?

No. the wheels will be spinning twice as fast. The plane will still go forward at the same speed. Unless there's enough friction in the wheel hubs to stop it moving forward. In which case it won't take off.

It's easy to see why it causes confusion though.

I thought in the original problem the conveyor belt continually matched the speed of the plane, so the plane goes forward at 10 mph, conveyor moves back at 10 mph therefore overall speed of plane through air (wind over wings) equals 0. Plane accelerates to 20mph, conveyor matches, plane through air = 0 and so on?

It has no affect the air movement though.

Can a Swan take off on a treadmill?

After it's broken your arm.

I think some trolls have crept into this thread! 😉

The arm is irrelevant. Can the swan take off?

No. Because it uses it's legs to get itself moving in the first place. The plane doesn't.

I thought in the original problem the conveyor belt continually matched the speed of the plane, so the plane goes forward at 10 mph, conveyor moves back at 10 mph therefore overall speed of plane through air (wind over wings) equals 0. Plane accelerates to 20mph, conveyor matches, plane through air = 0 and so on?

Read my re-stating of the problem near the start of this thread.

The conveyor belt won't be able to prevent the plane from moving forward, no matter what speed you run it at.

It could be whizzing backwards at 200mph and the plane would still be able to move forward along it and take off normally (provided the wheel bearings and tyres could handle it).

What about a waiter wearing roller skates on a teradmill bringing me my drink on a tray? How fast would he have to skate if the conveyor continually matched his forward speed? Would I get thristy? Would he spill the drink whilst frantically skating on the spot? Whats for lunch?

So can a swan fly if it hasn't got any legs?

Swan would take off, how do you think it takes off from a pond? Runs through the water? It uses the beating of its wings to provide both forward and vertical movement.

A swan can't take of from standstill vertically. I don't think so anyway. They have to be moving forward as far as I know. It would trip over as well. Is there a pond on the treadmill?

No, but the swan is carrying a family of american hamsters on their way to florida, and has had it's legs bitten off by a pike.

Those hamsters are not real americans – they're Mexican illegal aliens. The feds will be down on them like a ton of bricks.

What about a pair of conveyor belts beside each other running in opposite directions, so on the right hand side the wheels are doing full speed forward , and vice versa on the left, would that turn the plane in to a helicopter?

How many feds are equivalent to a ton of bricks?

I'm starting to feel sorry for the swan, even if it has broken someone's arm.

This is so passé.

Helicopters on turntables are the new big thing.

No! The engines are pushing it forward, not the wheels. It's broadly analogous to putting the plane on an infinitely long, infinitely smooth ice rink. A car couldn't move because the wheels would just spin (a la treadmill) but because a plane moves forward by throwing air out the back of the engines, it'll accelerate and take off normally.

Doesn't matter what the wheels are doing. In fact, if the system is considered to be ideal, you can set the treadmill going whatever speed you want at the very start and the plane won't move backwards – only forwards, under it's own engine power.

The tonne of bricks is an imperial measure of law enforcement, now superseded by the SI unit COP.

1 tonne of bricks = 30 COPs

For information another measure of law enforcement at the lower end of the scale is the ASBO equvialent to 0.3 of a microCOP or 0.3 e-6 COP's

Dammit – everyone always feels sorry for the swans, but they are the real menace here! Exploiting the mexican hamsters in an illegal slave trade.

I know a fed who can carry a ton of bricks – just not all at the same time.

🙂

Read my re-stating of the problem near the start of this thread.

The conveyor belt won't be able to prevent the plane from moving forward, no matter what speed you run it at.

It could be whizzing backwards at 200mph and the plane would still be able to move forward along it and take off normally (provided the wheel bearings and tyres could handle it).

okay, got it now. Ta

This thread is a perfect example of the futility of online discussion, for a start it's already been done three or four times on here alone. I thought the 100 hours I've spent on Final Fantasy IV were wasted… Chuff me.

So can a swan fly if it hasn't got any legs?

Maybe it can be fitted with a rollerskate like those dogs that get their hind legs cut off.

konabunny – Member

So can a swan fly if it hasn't got any legs?

Maybe it can be fitted with a rollerskate like those dogs that get their hind legs cut off.

I reckon a float a'la sea plane would be better…

Now then – could a plane LAND safely on a conveyor belt?

Right I'm happy about the swan now.

But the hamsters are they economic migrants or are they illegal drug mule hamsters? How much blow can and illegal drug mule hamster carry?

mule-hamster

man, that's sick – there's NO WAY you could mate a mule with a hamster (or is this some kind of teleporting genetic reassembly mix-up)

A swan could take off on a treadmill.

Although it wouldn't move forward under the power of it's feet, it would remain stationary untill eventually its wings would create enough lift through flapping to enable it to begin to move. It's feet are only in touch with the water briefly (or in this case, tredmill) and the wings do the majority of the work. Additionally, the swan doesn't take off by wind speed over it's wing, but by down force from flapping, so eventually it would lift.

Mind you, the speed of the tredmill would probably rip it's feet off when it touchs it as it approaches take off speed…