initial speed when it is dropped is 150 ft/s
now at the same moment the acceleration due to gravity is perpendicular to its velocity
so as we know that
now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity
while tangential acceleration at the same moment will be zero
so
now radius of curvature is given as
so the radius of curvature just after it is dropped is 703.125 ft