1. The problem statement, all variables and given/known data Here is the question along with my attempt: As you see in my second equation there are two unknowns, A_out and dm/dt. I think my problem is that I don't exactly understand the equation. dm/dt is the net mass flow rate. For example if dm/dt is a positive number then there is more flowing into the nozzle than there is flowing out. In other words there is a build up of mass in the nozzle? I guess this isn't possible since we have a nozzle and that is why in this case dm/dt = 0? Because that is the only other way I can think of doing this problem but I am not too sure. In what case could dm/dt be positive? I am guessing when there is a tank that can be filled... But how do I know that the nozzle doesn't have a small pouch where the mass can build on itself...? Also when they say "mass flow rate through the nozzle" is this dm/dt or is it the mass flow INTO the inlet nozzle? Thanks! Edit: for those who read through my solution attempt, there is a mistake in the last line where I did my conversion from 80cm^2 to 80m^2. the 100cm/1m needs to be flipped.