Circular Motion

At the topmost point, the equation describing the circular motion is,

mg - R = mrw^2
where R is th enormal raction
m is the mass of a passenger
g is the acceleration due to gravity
r is the radius of the circular motion
w is the angular speed of the motion

For the passenger to feel weightless, R = 0
hence, mg = mrw^2
i.e. g = rw^2
w = square-root[g/r] = square-root[10/(21/2)] s^-1 = 0.976 s^-1

Therefore, no. of revolution in one minute
= (0.976 x60)/(2.pi) = 9.32