Given:
The radius of curvature r = 7.4 m.
To find the minimum speed of roller coaster to avoid the passengers' fallout.
Step-by-step explanation:
Two forces act on the roller coaster, centripetal force and force due to gravity.
The condition to avoid passengers' fallout is

Here, the velocity is denoted by v.
The acceleration due to gravity is g = 9.8 m/s^2.
The radius is denoted by r.
On substituting the values, the velocity will be

The minimum speed of the roller coaster will be 8.51 m/s.