## Skill's weekend teaser

This is a discussion on Skill's weekend teaser within the General Trading Chat forums, part of the Reception category; Originally Posted by TheBramble If the conveyor is moving backwards (relative to direction plane is facing) at 180mph and that ...

 View Poll Results: What will happen? The plane will take off normally 25 40.32% The plane will remain stationary 32 51.61% The plane will run out of conveyor belt before it can take off 5 8.06% Voters: 62. You may not vote on this poll

Feb 22, 2009, 2:42pm   #91
Joined Nov 2007
Quote:
 Originally Posted by TheBramble If the conveyor is moving backwards (relative to direction plane is facing) at 180mph and that exactly equals the speed of the wheels on the plane, the plane has a realtive groundspeed (relative to ground under conveyor) of 0mph and an airspeed of 0mph.
Until the engines are switched on, then the plane has forward thrust.

Feb 22, 2009, 2:42pm   #92

Joined Nov 2008
Quote:
 Originally Posted by TheBramble Answer the questions as posed and you might find a glimmer of realisation. If the conveyor is moving backwards (relative to direction plane is facing) at 180mph and that exactly equals the speed of the wheels on the plane, the plane has a realtive groundspeed (relative to ground under conveyor) of 0mph and an airspeed of 0mph. If you were standing to the side of that conveyor in line with the plane - it would not be moving relative to your position. By your logic, that shouldn't matter and you'd both take off together I presume?
Until you understand that, due to the nature of a plane's construction and the fundamentals of its flight, it makes no difference whether the wheels are spinning or not, there is no hope for getting you to understand this problem.

 Feb 22, 2009, 2:43pm #93 Joined Nov 2008 Hmm, that's odd, Gecko posted the same answer as me at exactly the same time, seconds after you asked the queston... I wonder how that could be.
Feb 22, 2009, 2:44pm   #94
Joined Jul 2003
Quote:
 Originally Posted by Skill Leverage Yeah bramble you're right...until the engines are turned on... What is it you're not getting? Wheels dey do not affect de flight of de plane. Wheels spinny spinny, plane no movey. Jets they blow, airspeed increases, plane goes up in sky.
OK mate. Next time you're on a 747 ask the Captain to forgoe the normal procedures for takoff and just stick the brakes on hard - wang the engines up to full thrust, wait till airspeed somehow magically gets to 180mph and the release the brakes. Should go up a treat I reckon.

Let me know. I want to be there...

Feb 22, 2009, 2:44pm   #95

Joined Nov 2008
Quote:
 Originally Posted by Claudia123 Even I get it now thanks to some well worded responses. How would one of those Harrier things cope though - or is that for next Sunday ??
A Harrier has a 50/50 chance of taking off, I thought you knew that?

Feb 22, 2009, 2:45pm   #96

Joined Jan 2006
Quote:
 Originally Posted by TheBramble Answer the questions as posed and you might find a glimmer of realisation. If the conveyor is moving backwards (relative to direction plane is facing) at 180mph and that exactly equals the speed of the wheels on the plane, the plane has a realtive groundspeed (relative to ground under conveyor) of 0mph and an airspeed of 0mph. If you were standing to the side of that conveyor in line with the plane - it would not be moving relative to your position. By your logic, that shouldn't matter and you'd both take off together I presume?
You do not explain how the wheels get to 180mph. I'm figuring that if the wheels are spinning at 180mph (keeping the plane stationary) it means the plane is using a minimum amount of thrust to keep it stationary against the drag of it's wheels. In otherwords, the wheels are spinning due to the conveyor not due to the engines thrust. I could be wrong, but that's the way I figure it.
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Feb 22, 2009, 2:46pm   #97

Joined Nov 2008
Quote:
 Originally Posted by TheBramble OK mate. Next time you're on a 747 ask the Captain to forgoe the normal procedures for takoff and just stick the brakes on hard - wang the engines up to full thrust, wait till airspeed somehow magically gets to 180mph and the release the brakes. Should go up a treat I reckon. Let me know. I want to be there...
hahahahaha....

The brakes on the wheels are there to slow the plane down on landing mate. If he put them on during takeoff, then you are introducing FRICTION, which is another force to overcome.

The plane would still take off though, albeit with some burnt rubber.

Feb 22, 2009, 2:46pm   #98
Joined Jul 2003
Quote:
 Originally Posted by Skill Leverage Until you understand that, due to the nature of a plane's construction and the fundamentals of its flight, it makes no difference whether the wheels are spinning or not, there is no hope for getting you to understand this problem.
Great idea. Rip off the wheels. Put a float under the mother.

Put it in a stream that can be made to flow against the forward thrust of the plane so that it exactly cancels out forward movement. No wheels. OK? Logically same teaser. OK with that?

Where does the airspeed come form?

Feb 22, 2009, 2:47pm   #99
Joined Jul 2003
Quote:
 Originally Posted by Skill Leverage The plane would still take off though, albeit with some burnt rubber.
Unbelievable.

Feb 22, 2009, 2:47pm   #100

Joined Nov 2008
Quote:
 Originally Posted by new_trader You do not explain how the wheels get to 180mph. I'm figuring that if the wheels are spinning at 180mph (keeping the plane stationary) it means the plane is using a minimum amount of thrust to keep it stationary against the drag of it's wheels. In otherwords, the wheels are spinning due to the conveyor not due to the engines thrust. I could be wrong, but that's the way I figure it.
EXACTLY. And remember mate we are frictionless in this example, so there is no drag, and hence no thrust needed. But yes, even in real life you would still overcome this drag easily.

Feb 22, 2009, 2:48pm   #101

Joined Nov 2008
Quote:
 Originally Posted by TheBramble Unbelievable.
Yeah, it really, really is.

You are telling me that you actually believe that the brakes on two tiny wheels on a plane can overcome the thrust of four jet engines??????!!!

ROOOOOOOOOOOOOOOOOOOOOOOOOOOOOOFL.

Feb 22, 2009, 2:50pm   #102

Joined Nov 2008
Quote:
 Originally Posted by TheBramble Great idea. Rip off the wheels. Put a float under the mother. Put it in a stream that can be made to flow against the forward thrust of the plane so that it exactly cancels out forward movement. No wheels. OK? Logically same teaser. OK with that? Where does the airspeed come form?
Rip off the wheels and stick a plane on a runway.

Does it take off? YES IT DOES.

Putting a plane IN WATER against the current is completely different to having it on a conveyor belt... why? A stream pushing against a plane's hull DIRECTLY OPPOSES the thrust of the engines.

A CONVEYOR BELT ON THE WHEELS DOES NOT.

JEEEEEEEEEEEEEESUS

Last edited by Skill Leverage; Feb 22, 2009 at 3:02pm.

Feb 22, 2009, 2:51pm   #103
Joined Nov 2007
Quote:
 Originally Posted by TheBramble Unfortunately (for you) my answer was correct and it is based on experential knowledge (as a pilot) and an educational background in aerodynamics.
What sort of "pilot" are we talking about here - Have you flown 747's? Have you been a commercial or military pilot? Or did you just treat yourself to a PPL...

 Feb 22, 2009, 2:51pm #104 Joined Nov 2008 Oh, and if it was on a frictionless float, it would still take off as normal. Last edited by Skill Leverage; Feb 22, 2009 at 3:02pm. Reason: be nice you horrible man
Feb 22, 2009, 2:52pm   #105

Joined Nov 2008
Quote:
 Originally Posted by MrGecko What sort of "pilot" are we talking about here - Have you flown 747's? Have you been a commercial or military pilot? Or did you just treat yourself to a PPL...
Do Red Letter Days do flying lessons?