Political geography

In geography, what are "centrifugal forces" (or conversely "centripetal forces") and how can they affect the stability and national cohesion of a state (i.e., country)? Do you believe that a state/country that has stronger "centripetal forces" or a state/country that has stronger "centrifugal forces" is more likely to be stable and why? Alternatively, maybe you believe that centrifugal/centripetal forces no longer matter in today's world. Please provide specific examples and evidence to support your opinions.

source: https://www.pbs.org/wgbh/frontline/film/battle-for-hong-kong/