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  #3613  
Old 07-07-2014, 11:54 PM
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Quote:
Originally Posted by Benn0 View Post
Airflow over the aerofoil is a result of forward movement (unless there is a cyclone in progress).

There are many ways a conveyor belt can 'prevent' a plane moving forward, it may have cables holding the wheels, or some kind of brake mechanism on the wheels, it isn't important, the riddle just says this is a fact that it has this feature.

And now you are touching on the bit of the question that is ambiguous, what does it mean by speed? Ground speed measured at the wheels, or wind speed? If you measure speed at the wheels then nothing happens, if you measure wind speed then the plane moves forward at 200kph, the conveyor moves back at 200kph and the wheels spin at 400kph and the plane takes off.

There are a number of versions of the riddle, one specifically says speed at the wheels, another just says speed. If you google it you will come across pages and pages of views and calculations. Which ones you agree with will depend on your approach to solving it. The real answer is there is no answer....
Ok, lets put an end to this

Plane and conveyor belt. From Physclips: Mechanics with animations and film clips.

This breaks down the question in to two comparable but different versions

TL\DR

Question 1, yes the plane can take off

Question 2, yes the plane can take off, IF the conveyor is not spinning the wheels so fast that the miniscule bearing drag I mentioned earlier becomes large enough to cancel out the thrust generated.

/end
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  #3614  
Old 07-08-2014, 12:11 AM
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Re: WK2 DownUnder

Quote:
Originally Posted by vl_bt1 View Post
Ok, lets put an end to this

Plane and conveyor belt. From Physclips: Mechanics with animations and film clips.

This breaks down the question in to two comparable but different versions

TL\DR

Question 1, yes the plane can take off

Question 2, yes the plane can take off, IF the conveyor is not spinning the wheels so fast that the miniscule bearing drag I mentioned earlier becomes large enough to cancel out the thrust generated.

/end
Yep, slightly different wording in those ones, but I see a problem with his answer in Q2. The assumption is that a conveyor belt can only keep the plane stationary by very fast movement backwards. It is an assumption about the design of the control system the conveyor belt has not specified in the question. That answer actually seems to ignore the existence of a 'control system' altogether.
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  #3615  
Old 07-08-2014, 06:43 AM
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Re: WK2 DownUnder

Quote:
Originally Posted by Benn0 View Post
Yes, that is the conundrum.... there have been very long threads on the answer to that riddle, don't want to derail this one
That worked out well.
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  #3616  
Old 07-08-2014, 07:02 AM
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Old 07-08-2014, 07:55 AM
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Re: WK2 DownUnder

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  #3618  
Old 07-08-2014, 06:43 PM
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Re: WK2 DownUnder

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Originally Posted by SNUKE View Post
That worked out well.
Pfft, it's normally far worse than this when this topic is raised.
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Old 07-08-2014, 08:57 PM
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Re: WK2 DownUnder

Less geeks round these parts.
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  #3620  
Old 07-08-2014, 09:54 PM
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Re: WK2 DownUnder

The academics have got themselves bogged down in detail, as usual. The real issue is the design of the plane. As others have said, an aircraft relies on airflow over the wings for lift. Airflow can be achieved in three ways; by pushing the aircraft sufficiently fast through the air, by blowing air over the wings with a propeller, or a combination of both. On the conveyor, a turbojet plane or a pusher prop plane would not take off because there is simply no airflow over the wings. Propeller driven aircraft, be they turboprop or piston driven, with wing mounted engines, rely on the propellers to producing an airflow over the wings as well as pushing the plane through the air. The conveyor negates any forward motion leaving only the component of lift due to the propeller blowing air over the wing. Whether this component of lift is sufficient to get the plane gets off the ground depends on how much the designer has allowed for propeller produced lift and how much for forward motion produced lift.
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  #3621  
Old 07-08-2014, 11:17 PM
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Re: WK2 DownUnder

Guys I'm hopefully taking delivery of a MY14 JGC Limited at the end of the week (thought it would only be available end of August).

I have emailed the TSB regarding the CV boots to the dealer so that they can confirm that the build date lies outside the affected period and if it doesn't, I've told them they have to fix the shafts before I take delivery.

Assuming the shafts are all good, is there anything else I should do/ask before taking delivery? I plan on printing out the pre-delivery checklist I found on the forums and then running through all those points at the dealership to make sure it all checks out.

How do I check that the latest software/firmware updates have been applied? Can I find the latest versions for these somewhere so I can confirm?

Thanks all
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Old 07-08-2014, 11:24 PM
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Re: WK2 DownUnder

Quote:
Originally Posted by BobT View Post
The academics have got themselves bogged down in detail, as usual. The real issue is the design of the plane.....

Whether this component of lift is sufficient to get the plane gets off the ground depends on how much the designer has allowed for propeller produced lift and how much for forward motion produced lift.
Absolutely, or perhaps its a jump jet or a tilt rotor, the riddle doesn't say. With more detail an answer may be determined, but the question does what it is designed to, generate arguments.
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  #3623  
Old 07-08-2014, 11:25 PM
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Re: WK2 DownUnder

... and waste bandwidth
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  #3624  
Old 07-08-2014, 11:30 PM
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Re: WK2 DownUnder

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Originally Posted by sp_jeep View Post
Guys I'm hopefully taking delivery of a MY14 JGC Limited at the end of the week .....
Please stay on topic, this thread is about the nuances of words and physics.
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