Final answer:
As a submarine's speed increases, the magnitude of fluid friction or viscous drag it experiences also increases. This continues until the forces balance at terminal speed, where the submarine then travels at a constant speed.
Step-by-step explanation:
The question asks what happens to the magnitude of fluid friction acting on a submarine as the submarine’s speed increases. Fluid friction, also known as viscous drag, increases with the submarine’s speed. As a submarine moves faster, the drag forces acting against its motion will increase due to greater interaction with the fluid particles surrounding it. This is an application of fluid dynamics principles where the drag force experienced by an object moving through a fluid increases with velocity until a state of terminal speed is reached. At terminal speed, the object will move at constant speed because the drag force equals the driving force of the object. For a submarine, increasing speed results in higher fluid resistance, which may eventually stabilize once hydrodynamic forces balance.