# Calling maths/physics experts



## badger (Sep 3, 2002)

Was talking with some friends last night about guns and stuff, and I remember when I was at school being told that if you fire a gun hoizontally and at the same time drop a bullet from the same height, that both bullets would hit the ground at the same time.

My two friends said I was talking $hite, there is a small gentlemans bet riding on this! 

Was my school teacher having a laugh?

Please tell me I'm right!


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## coupe-sport (May 7, 2002)

It is true in a way - but only if its done in a vacuum, because then the only external influence is gravity and it affects both bullets in the same way. In air, air resistance comes into play and as drag is roughly proportional to the square of the velocity it has a large effect on the bullet fired from a gun.

James.


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## jgoodman00 (May 6, 2002)

Plus finding somewhere with enough open space to test this might be tricky


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## proeliator2001 (Feb 26, 2003)

Its true about drag being equal to the square of the speed but drag is acting against forward velocity only, assuming the bullet to be perfectly symmetrical (ie generating no lift or asymmetrical drag â€" therefore there is only gravity acting at 9.81 m/s^2 since no measurable lift is present) and its attitude during the entire trajectory is parallel to the ground. Therefore, if this idealised bullet is fired it should indeed hit the ground at the same time (within milliseconds anyway, I suppose the curvature of the earth comes into play, depending on how high the gun was fired). This is how marksmen can hit targets up to a mile away, by correcting for wind speed and drop height. I think though that the bullet will tend to slightly arc downward during flight and this will cause a quicker downwards motion but I honestly think that youâ€™d need to be talking a significant firing height above ground to truly notice that (ie shooting off the top of a mountain the bullet gets to the ground quicker than the dropped one due its arced trajectory speeding it downwards more quickly).


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## jgoodman00 (May 6, 2002)

Who is going to work out how far away it would be when it hit the ground then?


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## jampott (Sep 6, 2003)

Isn't the fired bullet quite likely to embed itself into something (or at least ricochet?) thus buggering up your calculations entirely....


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## PeteDolan (Jul 19, 2002)

Under theoretical conditions yes they would hit the ground at the same time. You would need a vacuum, a completly flat horizontal surface (remember the earth surface is curved),perfect gravity (i.e. no other extenal bodies affecting the gravitational force), and the bullet to be fired horizonally from a perfect gun. Under these conditions both bullets would hit the ground at the same time. I'm sure there are hundreds of other things to consider. Based on conditions on earth there is probably no way of proving the theory :-/

Pete


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## coupe-sport (May 7, 2002)

> Isn't the fired bullet quite likely to embed itself into something (or at least ricochet?) thus buggering up your calculations entirely....


*lol* - again in an ideal world, with an ideal bullet etc, in a vacuum etc


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## jampott (Sep 6, 2003)

.... and what if the dropped bullet actually hit your foot instead of the floor.....

so many things to take into account....

but even more importantly, can you fire off 3 bullets from a Manlicher-Carcano bolt action rifle from the Texas School Book depository in Dallas with INCREASING accuracy in a quicker time than the US Army's finest marksmen can't even reload in, AND have the evidence point to 4 shots being fired. In other words, does a bullet fired from the grassy knoll explode in the president's head at the same time as one fired from several storeys up?


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## coupe-sport (May 7, 2002)

[smiley=help.gif]


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## ag (Sep 12, 2002)

The theory is simply that the vertical acceleration component in the two cases is identical. Therefore they hit the floor at the same time.


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## christtopher (May 7, 2002)

> (remember the earth surface is curved)


Damn, I forgot about that.


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## Guest (Jun 7, 2003)

Tell me the height from which they are fired/dropped, and the speed at which the bullet is fired....and I'll tell you the distance away that the fired round lands, and the time it takes for them both to fall.....no probs. Â 
I'll even tell you the speed at which the fired round hits the floor if you like!! ;D ;D


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## jampott (Sep 6, 2003)

> (remember the earth surface is curved)


it is? would that explain why it always feels like I've got one leg shorter than the other......


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