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another physics question

scottm21166scottm21166 Member Posts: 20,723
edited April 2006 in General Discussion
I have been told....
if a rifle is fired down range on a level flight that bullet will hit the ground at the same time a same size bullet were dropped straight down from the muzzle...provided the bullet could be dropped at the exact millisecond the other left the barrel. some law of physics? anyone know?

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    Warpig883Warpig883 Member Posts: 6,459
    edited November -1
    R Lee Ermy fired a rifle that he bought on GB from Locust Fork at an attacking black bear and the bear ate the bullet and dropped a turd in the same amount of time it took someone to ruin the give away HappyNanoq was doing.
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    scottm21166scottm21166 Member Posts: 20,723
    edited November -1
    quote:Originally posted by Warpig883
    R Lee Ermy fired a rifle that he bought on GB from Locust Fork at an attacking black bear and the bear ate the bullet and dropped a turd in the same amount of time it took someone to ruin the give away HappyNanoq was doing.

    yes, but can you document the equation and repeat it? if not its just a theory and coincidence
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    DancesWithSheepDancesWithSheep Member Posts: 12,938 ✭✭✭
    edited November -1
    quote:Originally posted by scottm21166
    ...some law of physics? anyone know?

    I believe it is called gravity (g = 978.0495 [1 + 0.0052892 sin2(p) - 0.0000073 sin2 (2p)] centimeters per second squared at sea level at latitude p).
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    CubsloverCubslover Member Posts: 18,601 ✭✭
    edited November -1
    ^^^^True Statement ^^^^

    Scott, I KNOW that is a true law of physics, just don't know who's law.
    Half of the lives they tell about me aren't true.
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    cbxjeffcbxjeff Member Posts: 17,442 ✭✭✭✭
    edited November -1
    In a word - no. What we have here is the real world getting in the way of the equations!

    DWS, for sure, is right about the gravity thing. The problem is that once you fire the bullet, even though it on a horizontal path, other stuff (the real world with wind, I would think changes in air density during the travel, a pesky bumble bee, karma, etc) alter what really happens.

    Having said all that - if you dismiss the real world, DWS has it and the answer is yes.
    It's too late for me, save yourself.
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    Warpig883Warpig883 Member Posts: 6,459
    edited November -1
    quote:if you dismiss the real world, DWS has it and the answer is yes.

    I have never seen the world we call GB summed up so well. It is the hell we live in. Is there any hope?
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    nordnord Member Posts: 6,106
    edited November -1
    Simplest answer is that gravity will work on both with equal force. Thus, fired in a vacuum on a perfectly level surface from a perfectly horizontal tube, and a like bullet is dropped from the muzzle at the same time the other exits... They'll land at exactly the same instant.

    This won't happen in the real world, but it's a correct theory.
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    Warpig883Warpig883 Member Posts: 6,459
    edited November -1
    My wife would kick my * if I fired a bullet in her vacuum.
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    dcon12dcon12 Member Posts: 31,954 ✭✭✭✭
    edited November -1
    quote:Originally posted by Warpig883
    My wife would kick my * if I fired a bullet in her vacuum.


    Your wife has a vaccum? Don!!!![}:)][}:)][}:)]
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    Warpig883Warpig883 Member Posts: 6,459
    edited November -1
    I thing thats what is is. It sucks really goodhard.
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    stanmanstanman Member Posts: 3,052
    edited November -1
    Scott,
    I have been advised that the laws of physics do not apply where firearms are concerned.
    This is why a 180 gr. bullet fired from a WSM at 3000 fps and an 8.5 lb. rifle will have less recoil than the same bullet at the same velocity if fired from a .300 Win. and a rifle of equal weight.
    All that matters is powder charge, everything else be damned.
    So when the powder manufacturers develop a powder capable of launching a 500 gr., .458 cal. projectile at 3000 fps using only 3 grs. of powder we will be able to hunt cape buffalo with a virtually recoilless weapon no larger than a ball point pen.




    (Yes, this post is heavy on the sarcasm.)
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    JamesRKJamesRK Member Posts: 25,670 ✭✭✭
    edited November -1
    quote:Originally posted by Warpig883
    R Lee Ermy fired a rifle that he bought on GB from Locust Fork at an attacking black bear and the bear ate the bullet and dropped a turd in the same amount of time it took someone to ruin the give away HappyNanoq was doing.

    I thought the bear caught the bullet with his teeth.
    The road to hell is paved with COMPROMISE.
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    cbxjeffcbxjeff Member Posts: 17,442 ✭✭✭✭
    edited November -1
    883,

    Does your wife happen to have a single sister?!
    It's too late for me, save yourself.
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    Warpig883Warpig883 Member Posts: 6,459
    edited November -1
    quote:Originally posted by stanman
    Scott,
    I have been advised that the laws of physics do not apply where firearms are concerned.
    This is why a 180 gr. bullet fired from a WSM at 3000 fps and an 8.5 lb. rifle will have less recoil than the same bullet at the same velocity if fired from a .300 Win. and a rifle of equal weight.
    All that matters is powder charge, everything else be damned.
    So when the powder manufacturers develop a powder capable of launching a 500 gr., .458 cal. projectile at 3000 fps using only 3 grs. of powder we will be able to hunt cape buffalo with a virtually recoilless weapon no larger than a ball point pen.




    (Yes, this post is heavy on the sarcasm.)


    I think the trend is toward developing a .0001 diameter bullet traveling at 5000 fps and good for shooting everything from ticks of a guys neck to elephants.
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    scottm21166scottm21166 Member Posts: 20,723
    edited November -1
    ok, what I don't get is, if you ad more powder the bullet has further range and velocity say on a level plain a 22 short has a range of 1000 feet (its just for discussion) say it covers that distance in 1 second. now with stans 300wby mag the range has increased to 10,000 feet which now requires 3 seconds (more or less) so if a bullet is dropped from the 300 mag it still hits the ground in 1 second as would the 22...right?
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    1911a1-fan1911a1-fan Member Posts: 51,193 ✭✭
    edited November -1
    yes it is true

    take the velocity of a bullet, then consider the drop at 1,000 yards, some bullets will drop 6 feet or more in less than a the second that it takes to reach it's target

    there is a way of math to figure this out, but i have a headache
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    BlckhrnBlckhrn Member Posts: 5,136
    edited November -1
    quote:Originally posted by scottm21166
    ok, what I don't get is, if you ad more powder the bullet has further range and velocity say on a level plain a 22 short has a range of 1000 feet (its just for discussion) say it covers that distance in 1 second. now with stans 300wby mag the range has increased to 10,000 feet which now requires 3 seconds (more or less) so if a bullet is dropped from the 300 mag it still hits the ground in 1 second as would the 22...right?


    All things equal, yes. The point of aim for the 300 mag would need to be elevated for it to travel 10,000 feet. Also, air densities affect forward travel of a bullet significantly (exponentially) more than its downward travel.
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    fugawefugawe Member Posts: 1,540 ✭✭✭
    edited November -1
    Nord said it right. The two objects would hit simultaneously but only in a vacuum. In the real world there are other forces involved. Aerodynamics, the fact that the bullet is spinning at around 180,000rpm, curvature of the Earth over the distance fired, and maybe even the Coreolis effect. The direction that the bullet is launched could even be a factor. If you are standing on the equator and fire to the east the bullet gets roughly a 1500fps boost, increasing its centrifugal(or centripital) force and keeping it airborne slightly longer. If fired to the west the effect would be reversed. The effect of these forces would be difficult to measure but they will create a slight difference.
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    1911a1-fan1911a1-fan Member Posts: 51,193 ✭✭
    edited November -1
    you guys are truly rocket scientist

    tell us about bullet rise, you know on a ballistics table it states
    + {x} amount at 100 yards
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    scottm21166scottm21166 Member Posts: 20,723
    edited November -1
    quote:Originally posted by buschmaster
    quote:so if a bullet is dropped from the 300 mag it still hits the ground in 1 second as would the 22...right?

    yes.

    all the other stuff you talk about, long range shooting, it goes farther because you are tilting the rifle up to adjust for bullet drop. when you dial in a scope with a bullet drop compensator, you are adjusting the crosshairs down, so you have to tilt the rifle up to be on target. that's why the bullet flies for a longer time, because the trajecory is not initially flat.

    now that I think about it, say you are shooting from a bench. make the barrel totally level with the ground. say the ground is totally flat, like you're on a big parking lot.

    it can be said that no matter what you shoot, from a bb gun to a .50, the bullet will hit the ground at the same time. which is the same time if you just rolled a bullet off the bench and let it fall on the ground.

    say the bench is 3-1/2 feet off the ground. it will take 0.4666 seconds to hit the ground, so as long as the barrel is horizontal, no matter what cartridge you shoot it will hit the ground in 0.4666 seconds.

    ok, but then youre saying any bullet will hit the ground in less than half a second. so a muzzlevelocity of 3000 fps will hit the ground in just under 1500 feet from 3 1/2 feet? I guess that could be. considering a scope is sighted in and could be set to aim slightly above level
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    KSUmarksmanKSUmarksman Member Posts: 10,705 ✭✭✭
    edited November -1
    the reason is independant coordinates. Gravity only acts through the y-axis (down), it has no effect whatsoever on the horizontal flight. So if you fire a bullet level, gravity only affects the vertical velocity; air resistance affects horizontal velocity. So whatever time it takes for the bullet to fall a certain distance is the time it will be airborne. Multiply that time by velocity and you get the range.

    If you fire at an angle, then you also give the bullet some vertical component of the velocity (which will be sine of the angle of elevation multiplied by muzzle velocity). But the horizontal component will be reduced, it will become (cosine of angle times muzzle velocity).
    Of course taking air resistance into consideration will make the problem more difficult, one has to solve two coupled differential equations. This process gives me a huge headache and requires a computer [:D]
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    scottm21166scottm21166 Member Posts: 20,723
    edited November -1
    the good news is, your headache will go away...the badnews? Albert will not
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    matwormatwor Member Posts: 20,594
    edited November -1
    BUT, the bullet fired from the gun is traveling in such a direction that it is following the curve of the earth. SO, in theory the bullet would take just a smigdin' longer to hit the ground because the earth is getting further and further from the flat plane that the bullet was fired on. Yeah, I know, I just fired a bullet on a plane, which means I had a gun on a plane. Don't tell anyone.


    Edited for spelling.
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    1911a1-fan1911a1-fan Member Posts: 51,193 ✭✭
    edited November -1
    how far are you guys shooting that the curve of the earth would play a significant role?

    the height from the gun, and the height of when the bullet is dropped should be considered equal distance for this experiment, to consider anything else would be apples and oranges, it would be like shooting from top of a building and dropping the bullet from waist high, it would not factor the same
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    KSUmarksmanKSUmarksman Member Posts: 10,705 ✭✭✭
    edited November -1
    if you are close enough to observe a ground target directly, the curvature of the Earth is a moot point.


    The FA guys and the old school Navy gunners (from the days when the Navy used the gun for more than a hood ornament on an Aegis cruiser [;)] ) had to take into account the Earth's curvature, the coriolis (sp?) effect, etc, etc.

    On a side note:
    one of teh methods used to numerically solve differential equations, called the Runge-Kutta method, was developed by British artillery officers as a way to assist in trajectory calculations for range tables.
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    rogue_robrogue_rob Member Posts: 7,033 ✭✭✭
    edited November -1
    quote:Nord said it right. The two objects would hit simultaneously but only in a vacuum. In the real world there are other forces involved. Aerodynamics, the fact that the bullet is spinning at around 180,000rpm, curvature of the Earth over the distance fired, and maybe even the Coreolis effect. The direction that the bullet is launched could even be a factor. If you are standing on the equator and fire to the east the bullet gets roughly a 1500fps boost, increasing its centrifugal(or centripital) force and keeping it airborne slightly longer. If fired to the west the effect would be reversed. The effect of these forces would be difficult to measure but they will create a slight difference.

    +1
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    fugawefugawe Member Posts: 1,540 ✭✭✭
    edited November -1
    The fire control systems on Iowa class battleships used many of these factors in their firing solutions, including the distance the Earth rotated during projectile flight. By the way, these computers were mostly mechanical.
    Someone a lot better at math(or calculus) than me could probably figure out how far the Earth 'falls away' at, say, 1000yds. Any takers?[8D]
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    COLTCOLT Member Posts: 12,637 ******
    edited November -1
    ...working on it now, have the answer in a short...[^]

    EINSTEIN.jpg






    ani-texas-flag.gif
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    gibbsfeedgibbsfeed Member Posts: 8 ✭✭
    edited November -1
    It is absolutely correct. Gravity has the same effect no matter what the velocity.
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    scottm21166scottm21166 Member Posts: 20,723
    edited November -1
    so, does a bullet fly? a typical trejectory is an arc hits above where you aim at some point down range, right? I was always told this is because it spins and thus flys thru the air. if there is any aerodynamic displacement factor wouldn't that nulify laws of gravity?
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