Solve Bernoulli's Equation for Pressure at Throat of Converging-Diverging Nozzle

[MuzMond]

Homework Statement

Was flicking through a textbook and decided to give a question a try.

Flow through a converging diverging nozzle, determine pressure at throat picture attached.
Pressure at inlet = 50cm head, 4905PA
inlet dia = 2cm
throat dia = 1 cm
density of water = 1000kg/m^3
[/B]

Homework Equations

Bernoullis equation[/B]

The Attempt at a Solution

Cant find pressure at throat as both velocities are unknown,
Area of inlet = 3.142cm^2
area of throat = 0.785 cm^2.
We could make the outlet atmospheric, answer was around 7mH2o head.[/B]

 

[SteamKing]

1. Homework Statement
Was flicking through a textbook and decided to give a question a try.

This is generally not a good idea, unless you have studied all the material covered up to that point thoroughly.

Flow through a converging diverging nozzle, determine pressure at throat picture attached.
Pressure at inlet = 50cm head, 4905PA
inlet dia = 2cm
throat dia = 1 cm
density of water = 1000kg/m^3
2. Homework Equations
Bernoullis equation3. The Attempt at a Solution
Cant find pressure at throat as both velocities are unknown,
Area of inlet = 3.142cm^2
area of throat = 0.785 cm^2.
We could make the outlet atmospheric, answer was around 7mH2o head.

What you also need here, to find the inlet velocity, is known as Torricelli's Law:

https://en.wikipedia.org/wiki/Torricelli's_law

That's why you must study the figures included with the problem.