Hagan's Law is a principle in fluid dynamics that describes the relationship between the flow of a fluid and the pressure drop along a pipe. It states that the pressure loss in a pipe is proportional to the length of the pipe and the square of the flow rate. This means that as the flow rate increases, the pressure loss becomes significantly greater, which can impact the efficiency of fluid transport systems. The law is particularly important in engineering and design, as it helps engineers calculate the necessary pump power and pipe dimensions for various applications. Understanding Hagan's Law allows for better management of fluid systems in industries such as water supply, oil and gas, and chemical processing.