1. The problem statement, all variables and given/known data suppose we have a water reservoir with some pressure in it and a small hole through which the water exits. on the other side, there is just atmosphere. by increasing pressure on the "water side", the velocity of exiting water increases. what happens when pressure is large enough to propel the water stream at supersonic speed? 2. Relevant equations bernoulli's equation: (r = density; 1 - water tank, 2 - atmosphere) h1 + v12/2g + p1/rg = h2 + v22/2g + p2/rg h1, h2 = 0 (at the same level) v1 = 0 p1 = some high pressure p2 = 0 so v22 = 2p1/r 3. The attempt at a solution according to this equation, it would be possible to achieve both supersonic speed in air and in water. i know though, that strange things happen at that speeds, but have no clue what exactly is going on.