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#71
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Aerodynamic question for you engineers
Larry Dighera wrote in
: On Mon, 28 Jan 2008 07:20:09 +0100 (CET), Nomen Nescio wrote in : Your inability to distinguish rotation from translation. I'm unfamiliar with the term 'translation' as it refers to this issue. I presume you are referring to one of these definitions: (1) : a transformation of coordinates in which the new axes are parallel to the old ones (2) : uniform motion of a body in a straight line Can I impose on your MIT BSME to elaborate as to which definition it is to which you are referring? Thank you. What, you couldn't find anything in the FARs about it? Let me (and Merriam-Webster) take a guess first. Rotation is the action or process of rotating on or as if on an axis or center, and translation in this case is the movement or change of location of the CG. Am I helping or hurting? You're an idiot. Bertie |
#72
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Aerodynamic question for you engineers
Nomen Nescio wrote in
: -----BEGIN PGP SIGNED MESSAGE----- From: So, where's the flaw? Does anyone else see the flaw? Is there a flaw? Is Nescio here the only one who sees a flaw? A flaw he won't identify? I did identify the flaw. You can't seem to grasp it. Is this a serious, enlightening discussion or some sort of aviation Trivial Pursuit? A little of both, IF......you actually want to learn something. Try this one: You launch a missile at the moon. Halfway there you check it's free trajectory and find that it will hit dead center in crater X. Suddenly it explodes into a million pieces, all spinning off into space in all directions. What happens to the center of mass? Depends, Plain or peanut center? Bertie |
#73
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Aerodynamic question for you engineers
As I claimed earlier, if allowed thusters on a rigid body, I can make it rotate around ANY point. The table edge in my example could be replace by such a thruster. no you cant. an off centre force applied to a body resolves as a couple about the cg and a force through the CG the force through the CG pushes it along but the couple result in a rotation about the cg. in one of my old engineering texts the gentre of gravity is defined as the point within a body about which all forces resolve. the CG isnt a little sticker placed somewhere within a body. it is the centre of the mass of the thing and it varies with the movement of parts of that mass, be it evaporation of fuel in a carby which is burnt and jetisoned overboard as gasses coming out the exhaust or sweat evaporating from the brow of the pilot. all forces resolve around the centre of gravity of the body. it is an inherent attribute of all matter as seen through the eyes of an engineer. you really need to go out and fly a little aeroplane with not much inertia. (like a tailwind) you will see that all gusts and control inputs result in movements about the CG. it is what makes the behaviour predictable and the damn things flyable (and the predictive stress calculations possible) Stealth Pilot |
#74
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Aerodynamic question for you engineers
On Jan 28, 1:10 am, Nomen Nescio wrote:
-----BEGIN PGP SIGNED MESSAGE----- From: So, where's the flaw? Does anyone else see the flaw? Is there a flaw? Is Nescio here the only one who sees a flaw? A flaw he won't identify? I did identify the flaw. You can't seem to grasp it. Is this a serious, enlightening discussion or some sort of aviation Trivial Pursuit? A little of both, IF......you actually want to learn something. Try this one: You launch a missile at the moon. Halfway there you check it's free trajectory and find that it will hit dead center in crater X. Suddenly it explodes into a million pieces, all spinning off into space in all directions. What happens to the center of mass? I gotcha now. No problem. No more argument. Dan |
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