A high speed tubular ultracentrifuge with bowl radius of $100 \mathrm{~mm}$ and height $500 \mathrm{~mm}$ rotates at $20000 \mathrm{rpm}$ and settles starch particles (average diameter of $20 \mu \mathrm{m})$ on the wall. The ratio of centrifugal force to the gravitational force acting on the particle is____________

A high speed tubular ultracentrifuge with bowl radius of $100 \mathrm{~mm}$ and height $500 \mathrm{~mm}$ rotates at $20000 \mathrm{rpm}$ and settles starch particles (average diameter of $20 \mu \mathrm{m})$ on the wall. The ratio of centrifugal force to the gravitational force acting on the particle is____________

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