After another day of hard work you have reached the end of this subsection. Now is the point where we also have the answer of the question in the spark.

Right now, you should be able to explain to other students what momentum is and how it can be used on different systems, depending where the boundaries are set. You should be able to understand how the mass and energy balance are used, in order to help solve the momentum balance. With this knowledge, you can calculate velocities with the mass balance, pressure drops with the energy balance and ultimately forces with the momentum balance.

This subsection has been quite theoretical. In the next subsection, you will use this knowledge to put the theory to practice and calculate pressure drops in pipelines using the friction factor and the blasius equation.