This lecture covers the control volume approach in fluid mechanics, focusing on the Reynolds Transport Theorem and its application to mass and momentum conservation. The instructor begins with a recap of the fundamental laws of physics relevant to fluid flow, emphasizing the transition from Lagrangian to Eulerian perspectives. The discussion includes the continuity equation and Newton's second law, illustrating how these principles can be applied to real-world scenarios. The instructor presents an example involving jet engine thrust, detailing the necessary parameters such as inlet and outlet velocities, pressures, and areas. The lecture highlights the importance of choosing an appropriate control volume for analysis, demonstrating how this choice simplifies calculations. The instructor also discusses the significance of pressure differences in generating thrust, emphasizing that both momentum flux and pressure effects contribute to the overall force. Throughout the lecture, the instructor encourages students to practice applying these concepts to various fluid mechanics problems, reinforcing the power of the control volume method in analyzing complex systems.