Final answer:
The question asks for the maximum diameter of spherical dust particles that could be separated by a vertical air stream with a velocity of 10 m/s, considering a relative density of 2.8 for the dust. To answer this, we would need additional information such as air density and viscosity to apply fluid mechanics principles. Without this context, a precise calculation cannot be performed.
Step-by-step explanation:
The question pertains to the separation of dust particles from heavier granular material using a vertical air stream, a principle similar to that described in terminal velocity and fluid mechanics situations. To determine the maximum diameter of spherical dust particles that an air stream can carry, one has to consider factors such as particle density, air velocity, and the force of gravity acting on the particles.
Critical information such as air density, air viscosity, and the actual formula or equation to be used to calculate the maximum particle diameter is not provided in the question, and these are necessary to give a precise answer. Without this information, a general approach to this problem would involve using Stokes' law and the concept of terminal velocity, combined with the known properties of the dust particles, which include the given relative density and the air speed. However, without the additional information or context, we cannot complete this calculation accurately.