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airplane vs conveyor belt

Nov. 22, 2020, 9:19 p.m.
Posts: 2904
Joined: May 23, 2006

Push prop...

Nov. 23, 2020, 4:04 a.m.
Posts: 12942
Joined: Nov. 24, 2002

What about those with the prop on the nose.....anyways, 

Given the right design (wings and shit) could a plane with the prop on the nose fly backwards?

Nov. 23, 2020, 7:06 a.m.
Posts: 5866
Joined: April 10, 2005

Wouldn't the wings then be the wrong aerodynamic shape for backwards flight?

Nov. 23, 2020, 8:55 a.m.
Posts: 11158
Joined: June 29, 2006

Posted by: chupacabra

I am not sure why I posted this, but surely it had to be relevant to the question.

Nov. 23, 2020, 12:17 p.m.
Posts: 965
Joined: Nov. 23, 2002

Case 1: The conveyor belt is designed to exactly match the speed of the wheels

This is the problem! The wording of this quiz is wrong and makes it physically impossible. Divide this situation to several steps. At first, everything is just the same as in my explanation above. We apply thrust and we run the conveyor belt in the opposite direction. The wheel starts turning. As the plane moves forward – the conveyor belt accelerates. Keep in mind the preassumption “conveyor belt is designed to exactly match the speed of the wheels”. When the aircraft moves forward then its wheels have to travel further than the conveyor belt has moved back. But this is impossible in this situation. The conveyor belt is designed to match the speed of the wheel – so it will increase the speed. But the plane still moves forward – there is again a difference between the speed of the wheel and the speed of the conveyor belt. But we do not allow such situation! So we increase the speed of the conveyor belt!Actually, this is not a process that happens in steps – all of this happens simultaneously – the plane tries to accelerate and the conveyor accelerates to keep up with the wheels. Adding to the speed of wheels. And the wheels accelerate even more. So the conveyor belt…

It lasts until wheels and conveyor belt speed reaches infinity. Or until they reach the speed of light. If you wish to know what happens then – consult the screenwriters of Start Treck or Star Wars.The wording of this quiz is wrong! This case is impossible. It is impossible right from the very beginning where the preassumption is that the speeds will always match. If we know (and we know!) the forces applied on the plane we know that during the takeoff there is a huge imbalance of forces. So quoting the Newtonian law: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. The object will not stay motionless because we have unbalanced forces. So we can not design the conveyor belt to move at the same speed as wheels.

http://c-aviation.net/plane-conveyor-belt-explained-debunked/


 Last edited by: syncro on Nov. 23, 2020, 12:47 p.m., edited 1 time in total.
Nov. 23, 2020, 12:36 p.m.
Posts: 260
Joined: March 6, 2017

Simply put, the wheels are not providing forward propulsion so the speed of the wheels doesn't matter and have zero effect on the movement of the fuselage which IS providing forward propulsion via the engine

Nov. 23, 2020, 2:29 p.m.
Posts: 1287
Joined: Sept. 30, 2006

Posted by: three-sheets

So do you think a propeller pushes or pulls a plane?

Both?

https://en.wikipedia.org/wiki/Dornier_Do_335

Fastest piston engine fighter of WWII

Nov. 23, 2020, 2:45 p.m.
Posts: 11158
Joined: June 29, 2006

Posted by: syncro

Case 1: The conveyor belt is designed to exactly match the speed of the wheels

This is the problem! The wording of this quiz is wrong and makes it physically impossible. Divide this situation to several steps. At first, everything is just the same as in my explanation above. We apply thrust and we run the conveyor belt in the opposite direction. The wheel starts turning. As the plane moves forward – the conveyor belt accelerates. Keep in mind the preassumption “conveyor belt is designed to exactly match the speed of the wheels”. When the aircraft moves forward then its wheels have to travel further than the conveyor belt has moved back. But this is impossible in this situation. The conveyor belt is designed to match the speed of the wheel – so it will increase the speed. But the plane still moves forward – there is again a difference between the speed of the wheel and the speed of the conveyor belt. But we do not allow such situation! So we increase the speed of the conveyor belt!Actually, this is not a process that happens in steps – all of this happens simultaneously – the plane tries to accelerate and the conveyor accelerates to keep up with the wheels. Adding to the speed of wheels. And the wheels accelerate even more. So the conveyor belt…

It lasts until wheels and conveyor belt speed reaches infinity. Or until they reach the speed of light. If you wish to know what happens then – consult the screenwriters of Start Treck or Star Wars.The wording of this quiz is wrong! This case is impossible. It is impossible right from the very beginning where the preassumption is that the speeds will always match. If we know (and we know!) the forces applied on the plane we know that during the takeoff there is a huge imbalance of forces. So quoting the Newtonian law: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. The object will not stay motionless because we have unbalanced forces. So we can not design the conveyor belt to move at the same speed as wheels.

http://c-aviation.net/plane-conveyor-belt-explained-debunked/

^^  This.  Any forward movement violates the constraint and the question becomes invalid.  The only way the conveyor and wheel speed can match exactly is if the plane never moves forward, which means it can't take off.  End of story.

Nov. 23, 2020, 2:53 p.m.
Posts: 1137
Joined: Nov. 6, 2006

Posted by: chupacabra

Posted by: chupacabra

I am not sure why I posted this, but surely it had to be relevant to the question.

You should start a girls with guns and pickups thread.

Nov. 23, 2020, 3:24 p.m.
Posts: 1739
Joined: April 25, 2003

Posted by: three-sheets

So do you think a propeller pushes or pulls a plane?

Pretty sure the prop pushes air, the plane just goes in the opposite direction.

Nov. 23, 2020, 8:48 p.m.
Posts: 15485
Joined: May 29, 2004

Posted by: tashi

Posted by: three-sheets

So do you think a propeller pushes or pulls a plane?

Pretty sure the prop pushes air, the plane just goes in the opposite direction.

A propeller blade is essentially a wing. 

A wing creates an area of low pressure abouve the wing to create lift. 

This tells me that a prop pulls the plane. 

I mulled this over while circling for an hour waiting to land the other day.

Nov. 23, 2020, 8:52 p.m.
Posts: 965
Joined: Nov. 23, 2002

Posted by: three-sheets

Posted by: tashi

Posted by: three-sheets

So do you think a propeller pushes or pulls a plane?

Pretty sure the prop pushes air, the plane just goes in the opposite direction.

A propeller blade is essentially a wing. 

A wing creates an area of low pressure abouve the wing to create lift. 

This tells me that a prop pulls the plane. 

I mulled this over while circling for an hour waiting to land the other day.

newfie knowledge for the win

Nov. 23, 2020, 9:34 p.m.
Posts: 15009
Joined: Dec. 30, 2002

Posted by: syncro

Posted by: three-sheets

Posted by: tashi

Posted by: three-sheets

So do you think a propeller pushes or pulls a plane?

Pretty sure the prop pushes air, the plane just goes in the opposite direction.

A propeller blade is essentially a wing. 

A wing creates an area of low pressure abouve the wing to create lift. 

This tells me that a prop pulls the plane. 

I mulled this over while circling for an hour waiting to land the other day.

newfie knowledge for the win

And like a newfie... did he actually answer the question or just confuse the reader with some wordsmithery and skirt about it.

Because it still doesnt take off.

Nov. 23, 2020, 9:42 p.m.
Posts: 15009
Joined: Dec. 30, 2002

But speaking of props, I cant not share this.

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