1. The problem statement, all variables and given/known data http://i.imgur.com/4kztfIs.png 3. The attempt at a solution According to the solution, the max velocity is when the entropy of state 1 is equal to the entropy at state 2. Why is this the case? My friend says it is because the system is isentropic but I am still very confused. Is the system actually isentropic first of all?