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Post by laurel on Aug 9, 2010 17:16:01 GMT -4
For the record, I wasn't saying it was adequate quality to use in analysis because I don't know about these things. Rodin was demanding a URL for the footage and this is the best quality one I know of. I don't want to be misinterpreted here.
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Post by drewid on Aug 9, 2010 17:18:02 GMT -4
Rodin is claiming that there is a big discrepancy between the ascent time and the descent time. I've not got any tools with me this evening, but just looking at the video you can see that there really isn't, it's clearly pretty parabolic.
The biggest problem is going to be nailing down the centre point of the jump.
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Post by LunarOrbit on Aug 9, 2010 17:23:00 GMT -4
I'm not really an expert on such things, but I think the speed going up would be dependent on the amount of effort the astronaut put into the jump and the amount of gravity, whereas the speed going down is dependent only on the amount of gravity. Is that correct? I am pretty sure it is the same. Whatever force is applied upwards, is applied downwards. But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun?
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Jason
Pluto
May all your hits be crits
Posts: 5,579
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Post by Jason on Aug 9, 2010 17:23:10 GMT -4
Well I can see that gravity is a constant downward acceleration, but isn't the initial upward acceleration not constant? And wouldn't that mean that the upward trip might be of shorter duration than the downward trip? Or vice versa? I'm no physicist, I'm afraid.
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Post by drewid on Aug 9, 2010 17:23:23 GMT -4
I imagine the PLSS might complicate things a bit, being a semi-constrained mass. like jumping with a rucksack on it'll throw the visuals out a little.
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Post by theteacher on Aug 9, 2010 17:24:23 GMT -4
Do bear in mind that lots of members here also belong to BAUT. The amateur dramatics are unnecessary if your analysis is sound. OK I will cool it down. You are correct about the amateur part at least ;D Now then before we get to the downside is there a flaw in my analysis so far? Yes, I'm afraid there is. It was previously pointed out, that what is relevant is the center of gravity, which you ignored. Now the center of gravity shifts through the whole jump sequence because of the movement of the arm, and that fact affects the pattern of the movement in a way that makes your attention to the feet - or other points - pointless. Your job now is to identify the center of gravity at any point of the movement and prove, that the trajectory of that point is wrong. Before you do that any further speculation is utter waste of time and energy.
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Post by drewid on Aug 9, 2010 17:25:47 GMT -4
I am pretty sure it is the same. Whatever force is applied upwards, is applied downwards. But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun? Pretty much yes. Bullets have quite a high terminal velocity (no pun intended), people have been killed by falling bullets. (pretty rare though)
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Jason
Pluto
May all your hits be crits
Posts: 5,579
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Post by Jason on Aug 9, 2010 17:26:02 GMT -4
I am pretty sure it is the same. Whatever force is applied upwards, is applied downwards. But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun? I believe the Mythbusters busted that one too. Bullets fired straight up don't land with lethal speed, while if they are fired at an angel so they form a parabolic flight path then they can in fact still kill people.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Aug 9, 2010 17:26:12 GMT -4
I am pretty sure it is the same. Whatever force is applied upwards, is applied downwards. But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun? Look at my answer at the bottom of Page 5.
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Post by laurel on Aug 9, 2010 17:28:17 GMT -4
Bullets fired straight up don't land with lethal speed, while if they are fired at an angel so they form a parabolic flight path then they can in fact still kill people. But what kind of mean person fires bullets at an angel? Sorry, I couldn't resist.
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Post by drewid on Aug 9, 2010 17:28:55 GMT -4
Well I can see that gravity is a constant downward acceleration, but isn't the initial upward acceleration not constant? And wouldn't that mean that the upward trip might be of shorter duration than the downward trip? Or vice versa? I'm no physicist, I'm afraid. If you measure the trip from when the upwards force is no longer applied, i.e. when the feet leave ground, then it should more or less be a parabola, (given what's already been said about shifting centre of gravity).
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Post by LunarOrbit on Aug 9, 2010 17:30:59 GMT -4
Thanks, Bob. I figured air resistance played a role in how fast the bullet would fall, but I thought free falling objects have a maximum speed determined by the amount of gravity.
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Post by dwight on Aug 9, 2010 17:49:19 GMT -4
Should I even bother putting up the timecoded footage for the 4th time? I pretty much figured it was a waste of time after the first time. I have already on this thread been loosely called a liar because of my association. I can only imagine the near 1st gen resolution will only bring out the fire and brimstone once the new theory falls flat...
Perhaps I can set up an automated footage uploader to activate once a year...
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Post by homobibiens on Aug 9, 2010 17:50:55 GMT -4
I am pretty sure it is the same. Whatever force is applied upwards, is applied downwards. But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun? It would, if there were no air. Wouldn't have to be straight up, either, fire at an angle, and it would come back down at the same angle and same speed. (Again, if there were no air.) Edit - wow, the last five or so responses weren't here when I started typing!
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Post by capricorn1 on Aug 9, 2010 17:55:34 GMT -4
But if that is true wouldn't a bullet fired straight into the air fall back to Earth at the same speed that it left the gun? It would, if there were no air. Wouldn't have to be straight up, either, fire at an angle, and it would come back down at the same angle and same speed. (Again, if there were no air.) Edit - wow, the last five or so responses weren't here when I started typing! Can I just clarify something, I don't think it comes down at the same speed. It comes down from it's highest point in the same time it took to reach it........ Bob B can clarify this?
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