Step by step Fluid Momentum Example Problem with a Control Volume Moving at Constant Velocity. Reynolds Transport Theorem is explained in easy terms to help understand the most important parts.

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Fluid Momentum problems are Force problems so you'll need to draw free body diagrams and kinetic diagrams and use equations of equilibrium to find the force of the fluid jet acting on the cart to keep it moving at a constant velocity. The trickiest part is accounting for the speed of the cart to get relative mass flow rates entering and exiting the control volume. Another common mistake is using the wrong + or - sign when accounting for fluid entering or leaving the control volume.

TIMECODES
0:00 Draw Control Volume Perpendicular to Flow
1:35 Draw Free Body Diagram and Kinetic Diagram
3:02 Reynold's Transport Theorem Explained
3:23 Body Forces and Surface Forces
4:26 Reynolds Transport Theorem Integrals
7:12 Sign Convention for Fluid Entering a Control Volume
9:21 Find Mass Flow Rate using RELATIVE Velocity
12:21 Power is Force times Velocity