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Author Topic: Amiga.Org users encouraged to help debate  (Read 10659 times)

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Offline Cymric

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Re: Amiga.Org users encoraged to help debate
« on: February 26, 2006, 09:00:30 AM »
Since the determinig factor for lift-off is the speed of the plane versus that of the surrounding air, the plane cannot take off, as it is standing still with respect to said air. Question solved.
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Offline Cymric

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Re: Amiga.Org users encoraged to help debate
« Reply #1 on: February 26, 2006, 04:41:58 PM »
Quote
Boot_WB wrote:
5) The only thing the motion of the ground will accomplish is making the wheels rotate faster.

6) The plane will take off.

I trust you meant to insert a 'not' in there somewhere ;-).
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Offline Cymric

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Re: Amiga.Org users encoraged to help debate
« Reply #2 on: February 26, 2006, 05:08:42 PM »
Unfortunately for you, your reasoning is correct up until point 7. The plane does not take off, because there is no force imbalance. There is simply no net force in the vertical direction (a.k.a. lift), so the plane does not move upwards. That is the job of wings, alerons, flaps and slats: transform the horizontal motion of air passing over them into a vertical force which balances gravity, or exceeds it slightly (in which case Newton's Second Law stipulates an accelaration in the upward direction), or is slightly smaller (in which case there is accelaration in the downward direction).

That is also why loss of lift results in such catastrophic accidents. The plane still has lots of horizontal velocity relative to the air, but the areas which are responsible for lift don't do their job any more. The plane is then literally a brick due to impact on the ground within (I think) at most two or three minutes.

Later edit: Ack, ick, phooey. I never got the hang of the differences in torques in freely rotating bodies, or those which were powered to do so, when both are presented with a solid surface. Of course I am completely and utterly WRONG: The plane WILL take off. It's the same as when an airplane would be taking off from a completely iced-over runway. The wheels would just slip over the ice (and in fact, nearly stand still) so you'd lack the ability to steer unless you throttle the engines separately. But take off you will. The morale of the story: don't put a soapbox race car with JAT engine on those rolls used to test car performance in the lab, because you'll create one heck of a hole in the wall...
Some people say that cats are sneaky, evil and cruel. True, and they have many other fine qualities as well.