The correct answer is Bernoulli's equation Explanation & Key Takeaways: The basic equation of compressible flows are: • Bernoulli's equation • Momentum equation • Continuity equation • Equation of state Bernoulli's equation • The flow rate through a pipe is usually measured by providing a coaxial area contraction within the pipe and by recording the pressure drop across the contraction, which is the application of Bernoulli’s equation. • Bernoulli's principle can be derived from the principle of conservation of energy. • The Bernoulli's theorem states that, in a steady flow, the sum of all forms of energy in a fluid along a streamline is the same at all points on that streamline • Bernoulli equation represented in head form (the total energy per unit weight): \(\frac{P}{\rho g} + \frac{{{v^2}}}{{2g}} + h = Constant\) Bernoulli's equation represents energy per unit mass \(\frac{P}{{{\rho }}} + gh + \frac{{{1}}}{{2}}V^2 = C\)