Airplane on a Conveyor conundrum

[gwh200]

mwe an all,

theres a sh1t hot horizon on bbc 2 ............................al l about gravity

(questions later)

[nero279]

Can we just go back to basics for a moment?
When the plane attempts to move, it is powered by its own engines, yes?
And the conveyor belt. it moves in the opposite direction to the plane, but at the same speed, yes?
If so, then the plane will take off, but the wheels will be turning at twice their normal speed.. Or have I oversimplified things?

you're spot on Charlie ....................















































.............but it's fun watching everyone trying to over explain it and failing miserably

[Slugsie]

Of course it does! 10mph forward RELATIVE TO THE CONVEYOR travelling 10mph the other way results in 0. Its irrelevant how the force is delivered in this case, whether through wheels or through air thrust.

See above. If the aircraft is travelling at 10mph relative to the conveyor, the conveyor must travel at 10mph backwards. Leading to a relative speed between the two of 20mph. So the conveyor speeds up, and up, and up. Leading to infinity.

[progrob]

C'mon guys think about it, the fact that the wheels are freewheeling means there's no transfer of force between the conveyor and the body of the plane, the conveyor's force is acting on the wheels.


Conversely the propulsion generated by the planes engines does act on the body of the plain, meaning the plane must accelerate.


Relative to a fixed point or relative to the conveyor, airspeed/groundspeed, whatever, it has no bearing.

didnt think of wheels being freewheeling - I finally get it now!
would it work with a seaplane going up a fast stream?

[da SLUG man]

Of course it does! 10mph forward RELATIVE TO THE CONVEYOR travelling 10mph the other way results in 0. Its irrelevant how the force is delivered in this case, whether through wheels or through air thrust.

Soramad, the bullet will travel at 1201ft/s initially but will slow quicker due to the extra 600ft/s worth of drag.

Anyway, I said no more whoring for me, so I'm off to watch telly!

best one is that a bullet fired from a gun and a bullet dropped from the same height, will both hit the ground at the same time!!

[yoshie]

Listen stand on a tread mill on a sakteboard grab the front rail you stay in one place pull yorself forward and no matter what speed the tread mill is doing you and the sakteboard will move forwards off the front of the tread mill

WHY the thrust drive ect is not dependant on the wheels excerting a force on the tread mill the thrust comes from your arms pulling

The plane is driven forward by thrust not acting on the tread mill same as pulling with your arms

Your skateboard will fly off the front of the tread mill with you on it
Your plane will do like wise FLY

[KERRSURF]

nice to see the boffins go for it though.

[yoshie]

nice to see the boffins go for it though.

Yep made me chuckle

[Slugsie]

there does not need to a direct mechanical link beween the propulsion and
and the wheels.you frewheel down a hill,what would happen if halfway down the hill the road turned into a belt and matched your road speed,,you would slowly descend (by v=u+1/2 at^2) the hill as your mass would over come the negative net effect of the reversing road.

ie,
if the car is x and the road is y and we know x = y (car velocity and moving road speed) then adding something to x (the cars mass, acting not now downwards,but towards the front of the car,albeit at an angle) and we call that m

then we know x = y
but xm doesnt = y and can over come it , till x tends towards zero(when the moment of force once again reasserts itself straight down

OK, I think that the first part of what you say is in fact proving me correct.

If your car is rolling down a hill at 50mph, and suddenly the hill changes into a conveyor belt running at 50mph in the opposite direction, then you will continue on at 50mph down hill, but the wheels will suddenly be spinning at 100mph. If you want proof of that, look at the reverse situation of a car travelling at 51mph driving up a ramp suspended on the back of a lorry (ala Knight Rider, Italian Job) travelling at 50mph. When you get onto the ramp, the body of the car is still travelling at 51mph, if not the car would suddenly achieve 101mph, and disaster.

Getting back to the car rolling down the hill, if it was an aircraft with a take off speed of 50mph, it would be able to take off.

[gwh200]

[quote=nero279;404915]you're spot on Charlie ....................

not quite,explain this to me then.

how does an object move forward at 10 mph on a belt moving backwards at 10 mph ?

[yoshie]

Forget all that ######## read post 96 and end this

[KERRSURF]

[QUOTE=gwh200;404928]

you're spot on Charlie ....................

not quite,explain this to me then.

how does an object move forward at 10 mph on a belt moving backwards at 10 mph ?

see yoshies post.

[KERRSURF]

it simply moves at 20mph

[yoshie]

[QUOTE=gwh200;404928]

you're spot on Charlie ....................

not quite,explain this to me then.

how does an object move forward at 10 mph on a belt moving backwards at 10 mph ?

Read post96 thrust is not exerted from the wheels belt moveing is not relevant if the thrust is acting on something other than the belt the air or in my sakteboard the arm rail

[KERRSURF]

in this case the forward thrust from the engines.

remember the wheels are not powered so no matter how fast the conveyer goes they can still provide thrust as if from a static runway.