# Fluid mech energy formula

1. Sep 3, 2009

### custer

Why does $$Emec= P/\rho + v^2/2 + gz$$ ?
The units resulting from the three expressions are $$m^2/s^2$$
but unit for energy is supposed to be Joules? where does the mass go? If the three expressions were already divided by the mass then why Emec still remains as Emec?

2. Sep 5, 2009

### tiny-tim

Hi custer!

(have a rho: ρ )
Which book did you get that equation from?

The LHS should be the mechanical energy per unit mass.

(Compare it with ε, the internal energy per unit mass, or "specific internal energy").

See the PF Library on pressure and Bernoulli's equation

3. Sep 5, 2009

### custer

got it from a slide in my lecture note.. no wonder ;P
thank you :)