Skill's weekend teaser

[Claudia123]

but when the jetwash hits him, will he stay on the conveyor belt going round and round swearing at skill ?

 

[TheBramble]

Brambles do you still think that the jet engines can't make the plane fly if its on a conveyor belt runway? What would it take for you to change your mind?.

Sam, the plane is perfectly capable of flying off from the conveyor providing it can reach take off speed. But Skills says it can't ever do that. Check post #1. He says the plane can't make any forward motion at all.

 

[TheBramble]

And bear in mind, based on the current poll figures, you Flat-Earthers are still in a minority.

 

[MrGecko]

But Skills says it can't ever do that. Check post #1. He says the plane can't make any forward motion at all.

No he hasn't, that is only what you have inferred.

 

[MrGecko]

And bear in mind, based on the current poll figures, you Flat-Earthers are still in a minority.

Well I for one voted "stationary" but changed my position - I admitted I was wrong.

I would say that this is true for a few others, as well.

 

[Mr. Charts]

How about a cheer for the 3 voters who thought the conveyor belt would run out before take off?
True trader contrarians.

 

[Mr. Charts]

One of them must have been spanish89

 

[TheBramble]

No he hasn't, that is only what you have inferred.

Read it again. Carefully. For the constraint to hold there can be no forward motion. |If there is forward motion the constraint was not valid. Choose.

 

[TheBramble]

OK, Too much baggage (LOL) associated with the Boeing 747.

We are going to strap a Saturn V rocket in a horizontal position to a skateboard.

Same conveyor. Same constraint that any motion in the wheels on the skateboard will be exactly matched by the conveyor going in the opposite direction.

The Saturn V is still the most powerful rocket ever built. It doesn’t need aerodynamics or forward motion to take off – it just goes. So none of those complications. Forget frictionand any other real-world considerations.

Our Saturn V is lying on its side ready to go. If no other constraints were operating it would be off like a, well, like a rocket. Nothing would prevent it.

Except in our little theoretical example posed by Skills the rocket would have to stay absolutely in same spot due to precisely the same constraints placed upon the wheels-conveyor system that we have to apply in the 747 example. However impossible it might be to engineer this, if we accept the constraint as given, it’ll have exactly the same net result. Rocket wont move an inch.

 

[ezreddy]

Sam, the plane is perfectly capable of flying off from the conveyor providing it can reach take off speed. But Skills says it can't ever do that. Check post #1. He says the plane can't make any forward motion at all.

I think I have to applaud TheBramble for being able to milk this post as long as he has (he even got me to post again). Is it only me who realizes that TheBramble understands perfectly that a jet in this situation would take off; however, the postulation by Skill Leverage that the speed of the conveyor is the same as the speed of the jet's wheels but in the opposite direction cannot occur if you expect any forward movement from the aircraft (using a fixed reference point perpendicular to the direction of travel of the conveyor belt)? That is the point that TheBramble keeps making and he is correct (with the assumption that we are talking about linear velocity and not angular velocity). The situation that SkillLeverage's professors postulated cannot occur. As soon as the jet engine fires up, the wheels cannot go the same speed as the conveyor belt. I know SkillLeverage has acknowledged this and that TheBramble must have read this at least once. I just wish I could manipulate the market as well as TheBramble has manipulated us.

 

[searchlight]

I think I have to applaud TheBramble for being able to milk this post as long as he has (he even got me to post again). Is it only me who realizes that TheBramble understands perfectly that a jet in this situation would take off; however, the postulation by Skill Leverage that the speed of the conveyor is the same as the speed of the jet's wheels but in the opposite direction cannot occur if you expect any forward movement from the aircraft (using a fixed reference point perpendicular to the direction of travel of the conveyor belt)? That is the point that TheBramble keeps making and he is correct (with the assumption that we are talking about linear velocity and not angular velocity). The situation that SkillLeverage's professors postulated cannot occur. As soon as the jet engine fires up, the wheels cannot go the same speed as the conveyor belt. I know SkillLeverage has acknowledged this and that TheBramble must have read this at least once. I just wish I could manipulate the market as well as TheBramble has manipulated us.

Forget the markets. How is manipulating oneself feel.

 

[MrGecko]

exactly match the speed of the plane's wheels

So Bramble your view is that "the speed of the planes wheels" refers to translational velocity of, say, the wheels axle, as viewed by someone standing in the fixed reference frame

while

"the speed of the planes wheels" refers, in another case, to the speed at which the wheels are rotating around their axle, remaining stationary (bar the spinning) to the same viewer in the fixed reference frame.

Basically, translational vs. rotational kinetic energy.

??

NB: the statements "the plane takes off" and "Skill c0cked it up" are not contradictory to me

I don't think I could go back and figure it out without asking the OP which he means, unless I could prove that it didn't matter through the calculus...

 

[raysor]

Come on mate it's written in the poll. If you honestly have to ask whether the engines are running from the wording of that, then there's no hope for explaining the solution to you!

Has the pilot been drinking?

 

[ezreddy]

Forget the markets. How is manipulating oneself feel.

Not bad, but I would much prefer to be manipulated by others

 

[raysor]

No mate, this is wrong. If the plane is tugged quickly enough, it takes off; it is moving relative to the ground, no matter how fast the wheels of the plane/the belt are spinning.

This is the point you still fail to understand.

Surely relative to the air around the wings?

Surely the plane will stand still, unless the speed over the wings is moving at a speed equal to a plane's normal take-off speed.
If you were testing the downforce of a racing car (even a jet car), would it be any good putting the car on a rolling road and going at max revs? Surely the answer is no.
So having changed my mind a few times I would say the plane will not take off.

 

[Hotch]

The plane doesn't stay in the same place though, it moves forward long the run way. The wheels are spinning faster then they would normally when they take off (twice as fast).


...I think

 

[megamuel]

I also got it wrong initially (whish is evident on the first page of the thread!), I was even pretty slow to understand it and admit it, but I did, somewhere. I checked this question on the advanced physics forum (I am NOT a member!) and there are some real boffins on there. The general consensus seems to be that the plane DOES take off. Some people tried arguing that in order for the plane to fly, sufficient air needs to flow around the wings, and that if the conveyor went in the opposite direction to the wheels, the plane would remain stationary and there would be no air flow over the wings. These people went quiet once it was pointed out that actually, the jet engines create there own drive and push the air backwards and the plane forward. The wheels just spin freely on there axels. The conveyor could be moving backwards, forwards, constantly changing direction etc... the plane still takes off. The wheels have NO control over the plane.

Like I said before, if I am running on a treadmill with a jetpack on, and the treadmill matches the speed I am running... I can run faster, slower, or I can stop, as soon as I fire the jetpack up, I will fly off. It is using the air to propel me. I am willing to admit if I am wrong, as I already have done once, but as far as I am concerned,

THE PLANE TAKES OFF!!!!

 

[raysor]

I also got it wrong initially (whish is evident on the first page of the thread!), I was even pretty slow to understand it and admit it, but I did, somewhere. I checked this question on the advanced physics forum (I am NOT a member!) and there are some real boffins on there. The general consensus seems to be that the plane DOES take off. Some people tried arguing that in order for the plane to fly, sufficient air needs to flow around the wings, and that if the conveyor went in the opposite direction to the wheels, the plane would remain stationary and there would be no air flow over the wings. These people went quiet once it was pointed out that actually, the jet engines create there own drive and push the air backwards and the plane forward. The wheels just spin freely on there axels. The conveyor could be moving backwards, forwards, constantly changing direction etc... the plane still takes off. The wheels have NO control over the plane.

Like I said before, if I am running on a treadmill with a jetpack on, and the treadmill matches the speed I am running... I can run faster, slower, or I can stop, as soon as I fire the jetpack up, I will fly off. It is using the air to propel me. I am willing to admit if I am wrong, as I already have done once, but as far as I am concerned,

THE PLANE TAKES OFF!!!!

So what you are saying is that a 747 would take off from a runway with no wings?

The thrust, apparently, just overcomes the drag.

It is the lift that overcomes the weight of the plane: no air speed, no lift.
The plane stays where it is.
Unless of course you tilt the plane backwards, or use a Harrier.

 

[Hotch]

So what you are saying is that a 747 would take off from a runway with no wings?

The thrust, apparently, just overcomes the drag.

It is the lift that overcomes the weight of the plane: no air speed, no lift.
The plane stays where it is.
Unless of course you tilt the plane backwards, or use a Harrier.

What he's saying is that the jet pack and him running are separate, much like the jet and the wheels on the plane. His feet interact with the treadmill, as the wheels interact with the larger treadmill, the jet pack and jets however, do not.

I don't think it's a good example though.

 

[megamuel]

Ok a bad example maybe. My bad. Raysor - what drag are you talking about? And a 747 does have wing you pleb!