Practice portal › Laws of Motion › Dynamics of Circular Motion
Asked in CBSE PMT 1991 · Rotors, drums and turntables
Idea: in the rotating frame of the churn, everything feels an outward centrifugal force proportional to its own mass.
Milk is denser than cream, so for the same volume it needs a larger inward force to keep it circling.
In the rotating frame, the denser milk is flung outwards more strongly and collects at the walls.
The lighter cream is displaced by it and gathers near the axis.
The separation is therefore attributed to the centrifugal force in the rotating frame — the same principle a centrifuge works on.
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