It is true that the centripetal force is directed towards the center of the circle but in addition to the centripetal force there is another force called
centrifugal force which is reaction force. The centrifugal force is directed opposite to the centripetal force, i.e.,outward. It is due to this force that we never fall down even when we are upside down.
Technically, you are under the same downward acceleration at all times. When you are thrust up by the ride, it takes some time for the downward acceleration to stop the upward movement. That "some time" is your free upside-down ride.
Yes
The Demon in Great America, California. (that was my beginner roller coaster)
Upside down.
A part where the riders go upside-down.
A part where the riders go upside-down.
inertia
so it can get a little speed
Runaway Mountain does not go upside down.
It is a roller coaster that goes 60mph and it goes upside down, it also has some steep drops.
That is because the roller coaster is designed to accelerate you with enough force to experience more than 1G acceleration. When upside down you are being pulled down with 1G but up with more than 1G so net force is up, not down. Some rides give you 2-3 G up force.
The Tiger & Turtle is a roller-coaster at Magic Mountain Germany. It has steps and slopes that are climbed with human power - in other words, you walk on it. It is a 69-foot roller coaster, which puts the visitor 148 feet above the surrounding countryside of Duisbu, Germany. There is an upside-down loop on the coaster, but you can't actually walk on that part.
The Incredible Hulk roller coaster goes up-side down 4 times last for up to 7 seconds each time.