[Science Question] Will a plane take off?

This thread is well confusing :spangled:

The question wasn't 'How do planes fly?'

In this case the plane isn't trying to take off from a runway.

its all theory.... the conveyor belt would constantly speed up.

But its easier to imagine the conveyor belt as a frictionless surface, whatever its speed the plane would take off.... this is the case, the force friction will never equal the force of the planes thrust.

bastard - i've wasted half a mronign on this bullshit

Doesn't my first point kinda prove that the plane needs to move forward to take off? Which disproves the conveyor belt theory

yep, but one wing effects the aerodynamics of the other...

So you're saying it's basically the same concept as sitting ona skateboard with a conveyor spinning away underneath you and pulling on a rope that is attatched to a fixed point at the (off the) end of the conveyor?

I'd like to try this actually.. I can imagine it being impossible because of the conveyor matching the speed of the wheels at all times. Almost as if the pulling on the rope (thrusting of the engines) acts as an accelerator for the conveyor.

ps. Don't worry joe, i'm sure you've spent mornings doing a lot less.

the plane will move forward regardless of the speed of the conveyor belt.

No, it forms the question of 'Will the plane move forward on the conveyor?'

lol

yep the skateboard example is a good one.... the force of your arms will be stronger than the force of the conveyor belt

You're a condescending bastard sometimes.

I think you misunderstood my point (easy mistake ) I was saying that it does not matter whether the forward thrust comes from the wheels or the jets (i know it is not the wheels btw). If the conveyor belt is moving backwards at the same speed the plane is moving forward, the plane will not move at all relative to the air around it, therefore no lift will be generated and no take off possible.

I do and i don't see how.

If you were to move forward by pulling the rope, then surely the speed of the wheels in one direction is more than the speed in the opposite. Therefore the conveyor couldn't be matching the exact speed at all times in this case.

No?

It's a hypothetical question though.

Stop going on about the friction of the conveyor belt and whether it could possibly match the thrust of a plane. IF a conveyor belt was set to turn at exactly the same speed as the planes wheels, the plane would not move forward so would not take off.

lol pot calling kettle black old boy

explain why the plain wont move? that bit has me confused - what force would prevent it from moving?

As i said above, it's a hypothetical question. In reality the plane would probably move, because the conveyor speed would need to start from a stand still and increase with exactly the same rate as the plane's acceleration.

That's why i said a few posts ago that it's easier to think of the conveyor belt as a rolling road, rather than some power-driven belt.

Since when do roads roll?

Imagine if the plane were a hover craft - regardless of the speed of the belt it would move forward... the same logic works for the plane in theory.... however the wheels would probably lock up and not move at all... the plane would skid along at a slightly slower speed eventually taking off.

It's a totally different concept with a hovercraft. Hovercrafts 'float' on a cushion of air, with little or no friction from the surface they're floating on. So it wouldn't matter what direction or speed the belt was moving.

if you apply the brakes to a plane with its thrusts on full... it moves forward.

if the wheels are moving the same speed as the belt... it will be stationary... the thrust will still propel the plane forward.

andy if there is enough forward movement there will be lift - I understand the basics of aerodynamics.

I guess it's decided on the size of the engine/plane

I fail to understand how the same logic applis to a plane as it does to a hover craft. In this example we're given specific rules that state the conveyor matches the speed of the wheels at all time. A conveyor can't match the speed of a cushion of air that a hover craft uses whereas in this case, the speed of the wheels is matched.

With a plane, the thrust from the engines has to overcome the downward frictional force generated by gravity between the wheels and the ground by generating enough speed so that once the plane is going fast enough, the lift from airflow overcomes that force and the plane lifts off the ground and goes zooming off to sunny spain. However, because of the equal and opposite reaction law, if the conveyor is moving at the same speed as the wheels of the plane at ANY given point in time no matter how much thrust is applied, then the wheels simply cannot spin faster than the speed of the conveyor which makes a total ground speed of 0mph.

Agree or no agree?