FUN? Wow, some folks idea of "fun" absolutely amazes me. entertaining link origin however, the bullet ain't "falling" It starts out supersonic--M3 in the example above-- ----then slows.............initially, it meets resistance which pushes against the nose of the bullet, while negative pressure at the back of the bullet are both working to slow the bullet down. Please Register or Log in to view the hidden image! Then as it approaches the earth, the atmosphere gets denser and adds more resistance, while gravity is working as an opposing force. Assuming that all of that is correct: I ain't got a clue as to how to configure an equation which would quantify any of it. If you do, my hat is off to you! ......................................... When I was in Florida(circa '72-'73) there was a young man who was fond of jumping out of helicopters without a parachute. He remarked that his terminal velocity was slow enough to mitigate the dangers of free falling into water. So, he kept jumping from higher and higher. I wonder what ever happened to him?