Question

Investigate why blood is separated in a centrifuge rather than left to settle by itself.

Answer 1

The blood contains various substances which are almost same in mass so with gravitational force it doesn't get settled but due to high centrifugal force acting on it heavy particles in it get pushed to the bottom of the test tube

actually the centrifugal machine is made for separating this type of almost homogeneous mixtures

Answer 2

The technique to separate white blood cells from red blood cells in a centrifuge, which involve spinning. Blood is separated in a Centrifuge rather than settling by itself because the heavier parts of the mixture would not be possible too the edge.