1. The problem statement, all variables and given/known data Water is coming out of a water cannon at 25m/s, what is the pressure inside the cannon? 2. Relevant equations Bernoulli's (modifiedd): v = √(2gh) -> h = v^2/2g Prssure(liquid) : P = ρgh 3. The attempt at a solution Well, I wasn't too sure how a water cannon works, so I "made one" that is just a giant vat with a lot of water, and a hole at the bottom. I figured that for the water to come out at 25m/s, the height would have to be ~31m. h = (25^2)/2g So then I said, Pressure must be equal to ρgh, which is 1000 * 9.8 * 31m = 303,800Pa But the answer the book gives says its "4.125 x 10^5 Pa absolute." Any idea why my solution is incorrect?