Derive an expression for the theoretical discharge through a horizontal venturi meter and show how it must be modified to obtain the actual discharge.

Q1. Explain how pressure can be made in Bernoulli's equation from consideration of the forces and momentum changes as a fluid flows through a stream tube.

The pressure term ($P/\rho$) in Bernoulli's equation arises from the net work done by pressure forces on a fluid element as it moves along a stream tube. When applying Newton's second law (force equals mass times acceleration) to a fluid element, the difference in pressure forces acting on its upstream and downstream faces creates a net force. This net force causes a change in the fluid element's momentum. Integrating this force-momentum relationship along a streamline, alongside gravitational and inertial terms, reveals that the pressure term represents the energy per unit mass associated with the work done by these pressure forces.