Which factor primarily affects the speed at which water flows through a hose?

The diameter of the hose is the primary factor that affects the speed at which water flows through it. A larger diameter allows more water to pass through at once, resulting in a higher flow rate. This principle is based on fluid dynamics; as the cross-sectional area increases, the resistance to flow decreases, enabling water to travel more swiftly through a wider opening.

In contrast, while the length of the hose does impact flow rate, it is the diameter that has a more significant effect on the speed. A longer hose can result in increased friction loss, but if the diameter is large enough, it can greatly enhance flow rate despite the added length. The material of the hose can also play a role by affecting flexibility and resistance but does not directly control flow speed in comparison to diameter. The color of the hose is irrelevant to flow dynamics and does not influence how quickly water moves through it.