Problem 4-62 Centripetal acceleration

An astronaut in training is spinning around in a device that rotates at 30 revolutions per minute. (a) If the astronaut is \(7.5\; m\) from the centre of the device, what is the magnitude of the centripetal acceleration? (b) Express the answer in terms of "\(g,\)" the magnitude of the acceleration due to gravity.
[Ans. (a) \(74\; m/s^2\)   (b) \(7.6\; g\)]

The expression for centripetal acceleration is: 

(A)  \(a_c = v^2/r\)

(B)  \(a_c = 4\pi ^2r/T^2\)