To keep an object moving in uniform circular motion,
something must exert a centripetal force on it.
In the case of cars driving around a race track,
that centripetal force must come from the roadway
surface.
If the roadway is flat, then friction between the
tires and the road must supply all the centripetal force.
But if the roadway is banked, then some of the normal
force from the roadway can supply all (or some) of the
needed centripetal force.
One can derive the bank angle theta which is just
right for cars driving at speed v around a track
of radius r:
v^2
theta = atan ( ----- )
g*r
Centrifuges spin liquids at very high speeds around and
around; they can place very strong centripetal forces
on the liquids.
