This is more like personal homework and I have searched everywhere to find the answer to this with no luck. I was watching mythbusters re-runs the other night and the hurricane episode was on. They were trying to prove that straw could go through a tree in hurricane force winds. What perplexed me was the air cannon they used. Here is a little info on the setup: Setup "Jamie and Adam built an air gun to simulate the strongest possible hurricane wind: 318 mph. They were limited to 150 psi in the shop, so they compensated with the long barrel. The air gun: * Air compressor * 4' air tank (SCH 40 pipe) * pressure gauge * valve. Pilot-assisted diaphragm valve * 80' long barrel (1/2" diameter copper pipe) A test shot with a cotton ball at 8 psi went 321 mph, which was within 1% of their target speed." Why does an 80ft long barrel increase the velocity?? and is there some velocity to distance to pressure type equation to determine velocity? I always believed there would be a pressure drop due to friction, which would slow objects down over a distance? again I have searched everywhere for an answer to no avail. Thanks for your help in advance.