imported post
I don't need any citation for it, all I need is high school physics.
Ok, the acceleration due to gravity near the surface of the Earth is 9.8m/s squared.
That's about 32 ft/s squared.
If I stand next to you, and drop a bullet at the exact same time that you fire one out of a gun, into say an infinite open field, parallel to the gound,both bullets would hit the ground at the same time.
Why?
Gravity will pull on both rounds at exactly the same rate. The round in free fall will be falling at the exact same rate as the round fired by the gun. Horizontal speed has no effect, and cannot counteract the acceleration due to gravity. When the round that I dopped hits the ground, the round fired from the weapon will hit the ground at the same time. When mine hits the ground, yours has too.
Even if we started 5 meters off the ground, which is almost 16.5 feet off the ground, both rounds would hit the ground in one second. (That is half of the 9.8 m/s squared, since both object started at rest)
Also, a round fired either paralell to the ground, or at an upwards angle, will immediately start to lose speed due to air resistance, and this loss of speed will exponential as it travels and loses inertia.
I will simplify for you:
A 9mm round traveling at 300m/s (984 f/s) will only fly 165 meters (541 feet)before it hits the ground, if fired parallel to the ground. You could safely stand 600 feetdirectly in front of someonefiring the round, and it would not even reach you.
Now, increasing the fired angle will cause the projectile to go further, but it will be moving slower when it gets to it's target, due to deceleration from air resistance. The longer the round stays in the air, the longer it is in contact with the air causing the resistance, thus the slower it will be traveling when it arrives at it's final destination.
Now back to the whole firing into the air thing...
If you fire directly and straight into the air, the bullet will rise, stall, and then start to freefall. It cannot fall faster than it's terminal velocity, which is equivialant to the amount of air needed to stop it's acceleration, becuause it is not being propelled or acted upon by the explosive force of the gases that forced it down the barrel.This is also the amount of air it takes to START the object moving. Take a 9mm round, and place it on a table, and I bet you could blow hard enough to get it moving. That's with the added friction of the table it is sitting on, so imagine how little air it would take to cause that round to stop accelerating as it falls. Notice we are sayng make it stop accelerating, not make it stop it's motion altogether...
It's very similar to the old "Toss a penny off the Empire State Building" urban myth. While it may not be comfortable, and it may even hurt, the round cannon travel fast enough to seriously injure you coming straight back down on you.