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View Poll Results: Which Bullet will hit the ground first?
The bullet in his hand 31 28.70%
The bullet fired from the gun 4 3.70%
Both at the same time 70 64.81%
No idea. Stupid bloody question 3 2.78%
Voters: 108. You may not vote on this poll

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Old 07-06-2012, 07:05 PM   #81
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Not completely true...a bullet will travel so far that the earths tilt, sphere and whatnot don't impact the outcome even if all variables are included and not constants


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Other people have said this, but for the life of me I can't figure out how it doesn't impact the outcome. Can you explain?

At what threshold does it suddenly affect the outcome? If you are standing on a perfect sphere and take 2 steps, you are technically changing your vector of travel towards the sphere's axis. It's an almost imperceptible amount, but it's not zero. Basic rule of thumb is that the earth "drops away" 5 meters at 8,000 meters traveled. That's actually pretty substantial. So over the course of 500 or so feet of travel the earth will drop a measurable amount - probably something close to half an inch (just guessing and too lazy to try to crunch the real number) . . which means that the bullet fired from the gun has to fall that much farther before it hits the ground . . . and that takes time.
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Old 07-06-2012, 07:23 PM   #82
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I was randomly googling for stuff about curvature and ballistics and came across this cool link for naval ballistics - it's actually a pretty neat read. Stuff about how bullet spin causes the bullet to curve to the right, how maximum distance is often obtained by shooting above 45 degrees because of thinner air at altitude, etc. : http://www.hnsa.org/doc/firecontrol/partc.htm

It has this to say about curvature:

Quote:
C-20

THE PROJECTILE IN FLIGHT-EXTERIOR BALLISTICS

Other Factors Affecting the Flight of the Projectile (continued)

Because the earth's surface is curved, the target is not in the horizontal plane which is tangent to the earth at the gun. The greater the range, the farther the target falls below the horizontal and the line of sight is depressed below the horizontal. If the elevation angle were set to hit a target at the measured range in the horizontal plane, the projectile would fall beyond the target. Hence the elevation angle must be slightly reduced (depending on range) to correct for curvature of the earth.



Tabulated information is available on the correction to elevation angle required for various values of range. This correction is small for short range fire, but becomes appreciable as range increases.
So they actually have to factor in curvature in order to hit their targets when using naval guns. The shorter the range, the smaller the correction. There cannot be some magic distance where it does not become a factor whatsoever. No matter how far the bullet travels when shot from a horizontal plane, it must have farther to fall than a bullet dropped at the same point.

Last edited by brew; 07-06-2012 at 07:25 PM.
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Old 07-06-2012, 07:32 PM   #83
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Naval guns are a totally different class of projectile from an energy standpoint though. When you're shooting over the horizon then things get more complicated. We covered this exact bullet problem in my dynamics class and the answer on the test is they hit at the same time. It's a basic basic problem and the simple answer is we don't worry about the curvature of the earth. More often than not, things in physics are idealized (vaccum, flat plane, etc). It makes the math much easier to comprehend and gives a close enough answer, most of the time. Even the math we used to go to the moon is just an approximation. Granted, it's one hell of an approximation, but it's still not exact.
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Old 07-06-2012, 07:40 PM   #84
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Naval guns are a totally different class of projectile from an energy standpoint though. When you're shooting over the horizon then things get more complicated. We covered this exact bullet problem in my dynamics class and the answer on the test is they hit at the same time. It's a basic basic problem and the simple answer is we don't worry about the curvature of the earth. More often than not, things in physics are idealized (vaccum, flat plane, etc). It makes the math much easier to comprehend and gives a close enough answer, most of the time. Even the math we used to go to the moon is just an approximation. Granted, it's one hell of an approximation, but it's still not exact.
So then the answer is "the bullet dropped hits the ground first, but it's so close that for practical purposes we can say that they hit at approximately the same time."
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Old 07-06-2012, 07:44 PM   #85
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yeah you got it
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Old 07-06-2012, 07:49 PM   #86
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also for practical purposes, michael phelps isn't faster than most of the guys he beat
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Old 07-06-2012, 07:54 PM   #87
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also for practical purposes, michael phelps isn't faster than most of the guys he beat
"Wow - that was close! Who won?"


"Eh, well technically one of them was the winner, but it was so close that we'll just say 'they got to the finish at approximately the same time.' We need to find a couple of extra gold medals though."
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Old 07-06-2012, 08:00 PM   #88
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or just walk away knowing you're pretty much just as fast
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Old 07-06-2012, 08:04 PM   #89
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or just walk away knowing you're pretty much just as fast
And if anyone asks, you can say that you approximately beat Phelps.
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Old 07-06-2012, 08:07 PM   #90
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what's with you and beating? like i said, just you're about as fast.

kid, spend your life fighting and you will lose one day (may be a lot more than a medal).

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Old 07-06-2012, 08:46 PM   #91
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When you shoot a bullet straight up into the air it will come down slower than it went up.
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Old 07-06-2012, 09:17 PM   #92
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When you shoot a bullet straight up into the air it will come down slower than it went up.
False, if we're excluding air resistance
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Old 07-06-2012, 09:46 PM   #93
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False, if we're excluding air resistance
I shoot bullets on the earths surface. You?
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Old 07-09-2012, 12:11 AM   #94
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Here's one: A 2004 BMW 330xi and a ballpoint pen are dropped from within a vacuum at a height of thirty four meters. Both objects are suspended from a tower placed on the moon. Which hits first?
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Old 07-09-2012, 01:24 AM   #95
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^ Both at the same time. Same as Galilleo's theory and confirmed by a Nasa experiment on the moon wherein they dropped a hammer and a feather. They hit the lunar surface at the same time. There's a vacuum there on the moon.
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Old 07-09-2012, 01:29 AM   #96
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Old 07-09-2012, 02:35 AM   #97
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I am fascinated by this discussion. It highlights why I always did so much better in exams than most other people. I understood the essence of the questions and didn't confuse myself with extraneous facts that are not necessary.

The question I posed in the first post was prefaced by the comment "This is not a trick question" The more perceptive immediately understood that this was a simple physics problem and was never intended to include barrel rifling, earth curvature, air vortex, bullet spin etc, which if you add all these "tricks" may slightly effect the outcome.

It was merely a demonstration of Newtonian physics that dictate that gravity acts the same upon an object falling straight down or one propelled horizontally. This was the essence of the question and those people that included all the factors that may effect this outcome thought they were clever but in fact showed they were not clever enough to understand the essential question unless that question was so detailed as to exclude all other factors. Then of course it becomes boring and not a cute little succinct puzzle.

So many people ignored the statement "This is not a trick question". These people did not comprehend the INTENT of the question.
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Old 07-09-2012, 02:55 AM   #98
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Breyton-BMW,

Excellent moon video. Thanks. Had not seen that before.
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Old 07-09-2012, 02:55 AM   #99
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some of us think outside the box, i'm sorry
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Old 07-09-2012, 03:39 AM   #100
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depends. is it a .22 thats just going to stay in his scull? in that case, it would never touch the ground.
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