Which ones (if any) of these sentences are true?

[PeterBassett]

i totally see where you are all coming from.

but you are forgetting the weight of the plane on the wheels its a downward pressure.

You are going to have to explain how the weight of the aircraft stops it from rolling around on its wheels.

 

[Anonymous]

thats the whole point, the plane hasn't taken off, its very in conact with rolling ground.

If the plane was weightless then i would totally agree it would take off, but it isn't regardless of how free the wheel bearings are.

 

[Racers]

Hi, Mark

To cause drag on the plane there would need to be friction in the bearings causing heat.



Pete

 

[bugbear]

i totally see where you are all coming from.

but you are forgetting the weight of the plane on the wheels its a downward pressure.

You can press a roller skate down onto a belt sander as HARD as you like, and all that happens is the wheels go round.

BugBear

 

[PeterBassett]

Ok, now you agree that the wheels allow the the aircraft to roll freely on the conveyor, to move along it, just turn the engine on and accellerate to take off airspeed.

The conveyor is as long as a normal runway. Perhaps that has been missing in your thoughts?

 

[Anonymous]

tell ye what.

tomorrow before i get the workshop i will buy a matchbox car with free wheeling wheels and push it over a beltsander, i am not sure how i will do it in the interests of science ie weight the car down with a brick or something.

and i'll see what happens.

 

[Dibs-h]

thats the whole point, the plane hasn't taken off, its very in conact with rolling ground.

If the plane was weightless then i would totally agree it would take off, but it isn't regardless of how free the wheel bearings are.

The crux of it (for me anyway) is that such a wheel on a moving treadmill - the "leg" doesn't experience much if any in the way of horizontal force. The faster the treadmill - the faster the wheel spins. When you apply thrust to the plane - it will move forward.

I think if you held a small wheel on a treadmill (or a belt sander ) you'd experince for yourself that the horizontal component of force is virtually negligible. It doesn't increase with belt speed.

This very "conundrum" has resulted in some right argi-bargies on internet forums, so I'll bow out & I think we've done rather well. :lol:

Dibs

 

[PeterBassett]

tell ye what.

tomorrow before i get the workshop i will buy a matchbox car with free wheeling wheels and push it over a beltsander, i am not sure how i will do it in the interests of science ie weight the car down with a brick or something.

and i'll see what happens.

Please read what I wrote. You are so close to getting it.

Ok, now you agree that the wheels allow the the aircraft to roll freely on the conveyor, to move along it, just turn the engine on and accellerate to take off airspeed.
The conveyor is as long as a normal runway.

 

[Anonymous]

Honestly i really do get what you say, i just don't agree with you, (for now).

 

[PeterBassett]

Honestly i really do get what you say, i just don't agree with you, (for now).

I'll leave it there then.

 

[RogerS]

So Mark if you agree that a dangled plane will move forward then the wheels on the trolley are free-wheeling? Yes?

Same as the wheels under the plane...they free-wheel. They couldn't care less if the treadmill under them is stationary, moving forward or moving backward. The rotation of the wheels is irrelevant.

If the weight of a plane was an issue then as soon as the plane touched down, the wheels would lock solid according to your line of reasoning. Clouds of blue smoke! But that doesn't happen. There's a quick puff of smoke as the wheels are not rotating when the plane touches the ground. Then they start rolling and then the plane comes to a stop.

If weight was an issue then your car wouldn't free-wheel down a hill.

 

[bugbear]

I like that one, Richard.

Here's another. Imagine a treadmill large enough to stick a plane on. Now fire up the planes engines to take off speed and set the treadmill going until it also reaches take-off speed.

Question - will the plane take-off?

NO You are not allowed to ask this question. This question is the forum killer.

I used to frequent a motorbike forum and this question caused more arguments than anything else I've ever seen.

I really couldn't believe you when you wrote this. I apologise for doubting you!

Wow.

BugBear

 

[PeterBassett]

I've seen it before and I couldn't stop it! We truly are destined to repeat history.


A lot of it was my fault for not taking no for an answer...

Sorry everyone.

 

[RogerS]

Don't apologise...this is fun!

 

[Benchwayze]

Pete is right.

If you run fast enough, you can run up a downward moving escalator. (And vice versa)

So it boils down to how much power you can apply I guess.

Right?


If a lift is falling down a shaft out of control, could you save yourself by jumping up wards, just before it hits the buffers?

Serious answers please. and there's one answer I am looking for!


Hat-Coat-Door! :lol: :lol:

 

[PeterBassett]

Theoretically yes, practically no.

You would have to cancel out the downward velocity completely with the force of your jump.

Dependant on how long the lift had been falling, that could be a very high speed.

If you could generate enought force to jump with that velocity at just the right time you could survive.

However if you had muscles that powerfull (you dont) you would just break your legs with the force of the jump.

Superman could do it.

 

[SBJ]

I thinnk mythbusters did the lift thing too. If i remember correctly, the advice if you find yourself in that situation, was to lay on a fattie.

 

[PeterBassett]

if you find yourself in that situation, was to lay on a fattie.

As with so many other situations...

I'll get me coat.

 

[big soft moose]

If a lift is falling down a shaft out of control, could you save yourself by jumping up wards, just before it hits the buffers?

Serious answers please. and there's one answer I am looking for!


Hat-Coat-Door! :lol: :lol:

no , because you and everything else inside the lift are travelling at the same velocity - therefore all you will achieve by being inthe air in the lift when it hits the ground is to hit the floor a couple of seconds later at the same velocity.

lying on padding or a fat gett might help a bit but realistically you are pineappled whatever you do.

 

[RogerS]

If a lift is falling down a shaft out of control, could you save yourself by jumping up wards, just before it hits the buffers?

Serious answers please. and there's one answer I am looking for!


Hat-Coat-Door! :lol: :lol:

no , because you and everything else inside the lift are travelling at the same velocity - therefore all you will achieve by being inthe air in the lift when it hits the ground is to hit the floor a couple of seconds later at the same velocity.

lying on padding or a fat gett might help a bit but realistically you are pineappled whatever you do.

You haven't seen the size of my sister!