The setup I have is a water pump, with a pipe out leading to a nozzle of some sort. I know the mass flow rate of the water through the pump, and wish to calculate the exit velocity of the water from the nozzle. Which other variables do I need to know? Also, what dictates the limit to the exit velocity, as from conservation of mass, it would appear that simply making a tiny nozzle would give a high velocity. I'm fairly sure I'm missing something really simple and fundamental, but it's been a while since I've done this sort of thing. Cheers.