No it wont now quiet the lot of you

Why, did you put the parking brake on?

As mentioned earlier, thrust is provided by either a propeller or a jet engine. The amount of force (and therefore acceleration) provided is purely dependant upon the surrounding air, minus any friction from both the air itself and the surface on which the plane rests before it is flying.

The only reasons a plane has wheels and tyres are;
1 - to reduce the friction provided by the ground when taxiing/taking off
and
2 - to assist in controlled braking when landing.

The theory is completely different to a car, where the engine applies a rotational force to the wheels, which translates to a translational (forward) force where the tyres contact the ground. In a plane, the force is provided by the surrounding air, not the ground underneath the plane.

Therefore, the plane will take off and quaker's stick will go unused.

This post has been edited by camsmith: Feb 24 2006, 02:11 PM

The plane aint going anywhere

(until you turn off the belt)

and if you want 'workings' the plane's lift is created by the surrounding air being forced under the wing and pushing the plane up. Regardless of how fast the wheels are turning the plane isnt moving relative to the surrounding air

Imaging yourself standing on the wing....

Arnt you lot supposed to be clever?

This post has been edited by jamie: Feb 24 2006, 02:28 PM

Ok how about a different approach:

Imagine you could remove the wheels and replace them with anti-gravity devices so the plan just hovered a foot above the conveyer - would it be able to take of then? Of course - the engines provide thrust which gives the plane forward motion which moves air over the wings which provide lift. The action of the conveyor would have no effect on the planes ability to take off.

Assuming that the planes wheel brakes are off (as is normal for takeoff) they will only have a negligible effect on any motion of the plane with relation to whatever it is sitting on (a normal runway or a conveyor) so again the conveyors action will have no real bearing on the planes ability to take off. All that will happen by ramping up the conveyor speed to match the planes momentum is that the wheels will spin at twice the speed they would if it was taking off from an unmoving surface.

Alternatively, think about a matchbox car (I'm not talking about a wind-up car, simply a freewheeling model) on a similar (but smaller) conveyor.

The force applied to the matchbox car comes from your hand, not from the wheels on the conveyor. You would still be able to push the matchbox car off the end of the conveyor, regardless of how fast someone wants to make the conveyor move.

The planes lift is certainly not just being caused by air being forced under it and lifting it up - at least not in the sense that I think you wrote it (Jamie) - but I may have misinterpreted your explanation.

The wing is affectively 2 curved surfaces (the top and the bottom of the wing), the top is longer (it's a convex curve) and the bottom is shorter (a concave shape). The shape and the angle of attack of the wing causes the air to flow faster above the wing than below, and so the pressure above the wing is less than below the wing (Bernoulli's principle, relating to the pressure of air to its local velocity). This pressure difference causes a force, called lift that acts at right angles to the air-flow. Also both the upper and lower surfaces of a wing produces lift by deflecting air downward, which propels the flying body upward with an equal and opposite force (Newton's Third Law).

Going back to another point about flaps (BAHH!) -


So flaps only increase the properties of the wing to help give lift at lower speeds for control at take-off and landing, they aren't the sole reason planes take off (again I may have misinterpreted Paul's earlier post about flaps)

I would agree with camsmith on this one. Planes dont get propultion though the wheels so it doesnt matter that the direction of the ground is opposite to the thrust. The wheels will just spin at a faster rate than normal.

I am ment to know the answer to this question having discussed it with james but i am still unsure.

what you are suggesting would have to mean that the plane is not in contact with the ground at all, the plane cannot move foward via the wheels as they have been forced to stay in one plane (lets all agree on that) so what is forcing the plane to move faster than the convayer? for this is what has to happen, there has to be some motion for the air to pass under the wings! as its not motion from the plane moving along the ground as normal, what is it. The engine cannot move the plane faster than the conveyer, as gravity and the weight of the plane for it onto its wheels. are you suggesting that the engine counteracts the 1G created by gravity?
so if the wheels are counteracted by the conveyer you are suggesting that i plane can take of from standstill, on its belly without rubbing alone the ground?.

but to be honest with you if this where possible i am sure they would not have had to create harriors



and i dont agree with the matchbox thing

the matchbox thing doesn't work as your arm is counteracting the weight of the car and the gravities force as well as creating motion

WHAT?!! Anti gravity device!! In your example the plane has already taken off before yourve turned the engines on! There would be nothing stopping the forward or upward motion of the plane ie gravity...

and the argument suggests that no matter how fast you go the conveyer will keep up no matter what the speed is!

James/ cam are you saying that at the exact point of take off from the conveyer, the plane would accelerate from 0 to 600 miles per hour (or what ever the speed needed for take off Is) in an instant?

if you running on a treadmill with holding a handglider, i dont care if you run at 200 miles an hour, youre not taking off.

This post has been edited by jamie: Feb 24 2006, 03:26 PM

OK, so now, instead of using your hand to push the car, strap on a jet engine that provides the same amount of force, purely horzontally. The car will still fall off the end of the conveyor.

And Jamie, takeoff is closer to 150mph, not 600. but takeoff speed is irrelevant (except to determine the length of runway required), as is the speed relevant to the converyor. The only thing that matters to the plane is airspeed.

This post has been edited by camsmith: Feb 24 2006, 03:28 PM

which was my point. AIRSPEED, not converyer speed

The running on a treadmill is again not a fair comparison, because thrust is provided by contact with the ground, not by force on the surrounding air. Hence, the matchbox car example.

Once you get where I am coming from there, now replace the matchbox car with a similar scale model plane, complete with jet engine.


To ask you another question... what creates airspeed on a plane?

This post has been edited by camsmith: Feb 24 2006, 03:33 PM

If the planes 'speed' is being matched and conteracted by the speed of the conveyer, the plane isnt going anywhere, no air is being pushed under the wings so how does the plane achieve lift?

who's got that stick?