What is the relationship between flow velocity and friction loss in hoses?

The option stating that friction loss increases with the square of the velocity is correct because it reflects the principles of fluid dynamics as they relate to the movement of water through hoses. When water flows through a hose, it experiences resistance due to friction along the interior surfaces of the hose.

According to the Darcy-Weisbach equation, which is used to calculate head loss due to friction in a pipe, the friction loss is proportional to the square of the flow velocity. This means that if the flow velocity doubles, the friction loss doesn't just double; instead, it increases by a factor of four. This principle emphasizes the significant impact that flow velocity has on friction loss, particularly in firefighting operations, where efficient water delivery is crucial.

Understanding this relationship is vital for fire service pump operators because it directly influences pump selection, required pressure calculations, and the overall effectiveness of fire suppression efforts. When designing attack lines and considering the flow of water through hoses, knowing that higher velocities lead to exponentially higher friction losses helps operators make informed decisions regarding hose diameter, length, and pump operation to ensure optimal water delivery to the fire scene.