Question

Bernoulli's theorem is based on :

• A. conservation of mass, energy and momentum
• B. conservation of momentum
• C. conservation of mass
• D. conservation of energy

Answer 1

Answer: (D)

Bernoulli's theorem states that when an incompressible and non-viscous liquid (or gas) flows in stream-lined motion from one place to another then at every point in its path the total energy per unit volume
(i.e., pressure energy $+$ kinetic energy $+$ potential energy) is constant.
That is $P+\frac{1}{2} \rho v^{2}+\rho g h=$ constant
Thus, Bernoulli's theorem is in one form, the principle of conservation of energy for-a flowing liquid (or gas).
Dividing the Bemoulli's equation be $\rho g$. we have
$\frac{P}{\rho g}+\frac{v^{2}}{2 g}+h=$ constant
In this expression $\frac{P}{\rho g}$ is called the 'pressure head', $\frac{v^{2}}{2 g}$ the 'velocity head' and $h$ the 'gravitational head'.