View Single Post
Old July 13, 2013, 09:49 PM   #50
JohnKSa
Staff
 
Join Date: February 12, 2001
Location: DFW Area
Posts: 24,930
Quote:
An average bullet weighs less then a 1” hail stone.
Terminal velocity is a function of drag which means that density figures heavily into the equation. A 1" hail stone has a much lower density than a bullet and therefore has a much lower terminal velocity.

By the way, the figures I provided in my post (velocities and energy levels) were from actual testing (bullets fired in the air) done by the U.S. army many years ago, not from simulations or calculations.
Quote:
So you're saying that an object doesn't gain in velocity when falling, at 32.2 feet per second, squared? In other words, it doubles the speed every second, and that a bullet high in the air, would not hurt you?
A falling object accelerates until the force of gravity equals the frictional drag of the object as it moves through the atmosphere. Then it will stop accelerating since the forces are balanced. The resulting velocity is called the terminal velocity and the object won't fall any faster than its terminal velocity no matter how much farther it falls. In fact, as it gets closer to the ground, the air density increases so it the terminal velocity will actually drop slightly as the object approaches impact.

A heavy, aerodynamic object will accelerate to a much higher terminal velocity than a light object that has poor aerodynamics. That's why a rock or a dart falls much faster than a leaf or a ball of paper.

From your quote, this is the critical piece of information you need to focus on:

"...all results below will be quite inaccurate after only 5 seconds of fall..."

Quote:
However, a 30-06 can travel to 10,000 feet, or 3048 meters. It would take it 24.9 seconds to fall, and be traveling at 546.2 MPH, or 801 FPS.
This is a good example. Since the object is falling much longer than 5 seconds, using the freefall velocity figures (freefall figures assume no atmospheric drag) are very inaccurate. Experimentation has shown that the terminal velocity of a .30-06 bullet is around 300-400fps if it remains spin stabilized and falls back to earth base first or is much lower--about 150fps--if it does not remain stabilized and falls back to earth tumbling.
__________________
Do you know about the TEXAS State Rifle Association?
JohnKSa is offline  
 
Page generated in 0.02697 seconds with 8 queries