4. A suspended particle falls through a height H cm in water in t minutes. If the viscosity of water is ? and specific gravity of the particle is G, the diameter of the particle is (where M is a constant factor)
9. If the natural moisture content, the liquid limit and plastic limit of a soil sample are stated as 30.5%, 42.5% and 22.5% respectively, the ratio of liquidity index and plastic index, is