A flying-saucer shaped fairground ride is rotating in a horizontal plane. If the rider’s circular path has a radius of 8 m, at how many revolutions per minute the ride should spin in order for the rider to feel a centripetal acceleration of about 1.5 times Earth’s gravitational acceleration?

Ac = 1.5 g = approximately 15 m/s^2

Ac = omega^2 r
so
omega^2 = 15/8

omega = 1.37 radiaans/second

2 pi radian /rev
so

.218 revs/sec
times 60 s/min = 13 revs/min