ANS:A - Continuity equation

An ideal flow of a liquid obeys the Continuity equation. The Continuity equation is a fundamental principle in fluid mechanics that states that the mass flow rate of fluid in a pipe remains constant along the length of the pipe when there is no source or sink of fluid along the pipe's length. It expresses the conservation of mass for an incompressible fluid flowing through a pipe or conduit. Mathematically, the Continuity equation is expressed as: A1​⋅V1​=A2​⋅V2​ Where:

• A1​ and A2​ are the cross-sectional areas of the pipe at points 1 and 2, respectively,
• V1​ and V2​ are the velocities of the fluid at points 1 and 2, respectively.

The Continuity equation ensures that the flow of fluid remains steady and consistent throughout the pipe, without any buildup or depletion of fluid mass. While the other laws and principles mentioned—Newton's law of viscosity, Newton's second law of motion, and dynamic viscosity law—are all fundamental principles in physics and fluid mechanics, they do not describe the behavior of an ideal flow of a liquid as comprehensively as the Continuity equation does in terms of mass conservation and flow dynamics.