7. A sand mixture was screened through a standard 10-mesh screen. The mass fraction of the oversize material in feed, overflow and underflow were found to be 0.38, 0.79 and 0.22 respectively. The screen effectiveness based on the oversize is
Correct Answer: assumption that all particles in a single fraction are equal in size, is not needed.
9. In a mixer, the quantity, (v. L/D) is termed as __________ number(where, v = longitudinal velocity of material, L = length of the mixer, D = diffusivity in axial mixing).