Answer:
The answer is Linear Speed and centrifugal force.
Explanation:
The reason the coin in the center stays still compared to if it was on the edge is the diference in linear speed that depends on the rotational center distance.
In other words, the coin closer to the center is submitted to a low centrifugal force because it's spinning slower than the edge, and the coin closer to the edge is submitted to a higher centrifugal force because its spinning faster than the center.