Question

At t1 = 3.00 s, the acceleration of a particle moving at constant speed in counterclockwise circular motion is a1=(3.00m/s^2)i hat +(9.00m/s^2)j hat. At t2 = 5.00 s (less than one period later), the acceleration is a2=(9.00m/s^2)i hat -(3.00m/s^2)j hat .The period is more than 2.00 s. What is the radius of the circle?