Small solid particles of diameter $d$ and density $ho_{s}$ are carried horizontally by an air stream moving at velocity $V$. The particles are initially at a distance $h$ above the ground, and you want to know how far they will be carried horizontally before they settle to the ground. To find this out, you decide to conduct a lab experiment using water as the test fluid.

(a) Determine what variables you must set in the lab and how the value of each of these variables is related to the corresponding variable in the air system. You should note that several forces act on the particle: the drag force due to the moving fluid, which depends on the fluid and solid properties, the size of the particle and the relative velocity, and the gravitational force, which is directly related to the densities of both the solid and the fluid in a known manner.

(b) Is there any reason why this experiment might not be feasible in practice?