Final answer:
Mechanical centrifugal collectors are not suitable for the collection of very fine particles because these particles lack sufficient inertia to be separated effectively by the centrifugal force.
Step-by-step explanation:
Mechanical centrifugal collectors use the principle of inertia to separate particles from a fluid stream. These devices, including centrifuges, function by spinning the fluid, causing particles with sufficient inertia to move away from the center of rotation due to their mass, and collide with the walls of the collector.
Given the nature of this separation process, mechanical centrifugal collectors are not suitable for the collection of very fine particles. This is because very fine particles do not have enough mass and, therefore, inertia to be affected significantly by the centrifugal force; they may remain suspended in the fluid and not be captured effectively.