Really, the only difference is that this is a downward-curving path with the center of this circular curve below the slide instead of above. (Once again, the gray C-shape represents the path of the rider on the slide and the circular trajectory of their body, and the dot is the center of the circle.) That means the centripetal acceleration is also in the downward direction and towards the center of the circle.
Since the acceleration switched directions, the normal force (N) has to be less than the radial component of the gravitational force, which is pulling the person downward toward the Earth. What happens when the normal force gets smaller?
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