A delayed unit step function is defined as $$$u\left( {t - a} \right) = \left\{ {\matrix{ {0,} & {t < a} \cr {1,} & {t \ge a} \cr } } \right.$$$

Its Laplace transform is ____________.

The present population of a community is 28000 with an average water consumption of 4200 $$m^3/d$$. The existing water treatment plant has a design capacity of 6000 $$m^3/d$$. It is expected that the population will increase to 44000 during the next 20 years. The number of years from now when the plant will reach it's design capacity, assuming an arithmetic rate of population growth, will be

Most of the turbidity meters work on the scattering principle. The turbidity value obtained is expressed in

The ratio of saturated unit weight to dry unit weight of a soil is 1.25. If the specific gravity of solids (G_s) is 2.65, the void ratio of the soil is