A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m<sup>3</sup>) is to be fluidised by water (density 1000 kg/m<sup>3</sup>). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is

Correct Answer: 4.4 KPa