Q.What are the energies possessed by a liquid? Write down their equations.

A liquid in steady flow simultaneously carries three distinct kinds of mechanical energy. (i) KINETIC ENERGY: for a mass m of liquid moving with speed v, $\text{KE}=\tfrac12 mv^2$; per unit mass this is $\tfrac12 v^2$, and per unit volume (multiplying by density $\rho=m/V$) it is $\tfrac12\rho v^2$. (ii) POTENTIAL ENERGY: for a mass m at height h above a chosen reference level, $\text{PE}=mgh$; per unit mass this is gh, and per unit volume it is $\rho gh$. (iii) PRESSURE ENERGY: this is the energy a fluid acquires purely because pressure pushes it along. Since force = pressure times area, the work done pushing a volume V (cross-sectional area A) of fluid through a distance d is $F\times d=(PA)\times d=P(A\times d)=PV$, so the PRESSURE ENERGY of a fluid volume V at pressure P is $E_P=PV$; per unit mass this is $E_P/m=PV/m=P/\rho$ (using $m=\rho V$), and per unit volume it is simply P. These are exactly the three terms whose SUM -- pressure energy, kinetic energy, and gravitational potential energy, all taken per unit mass -- Bernoulli's …