You have a sample of crushed coal containing a range of particle sizes from 1 to $1000 \mu \mathrm{m}$ in diameter. You wish to separate the particles according to size by entrainment, in which they are dropped into a vertical column of water that is flowing upward. If the water velocity in the column is $3 \mathrm{~cm} / \mathrm{s}$, which particles will be swept out of the top of the column and which will settle at the bottom? (SG of the solid is 2.5)