A ball P has a mass m = 3 kg. The ball is lifted up the semicircular hill with racins (L6m by the arm OA which pivots at point (0. The center of the semicircular hill is at point O as shown. The arm maintains a constant angular velocity e =05 rad/s in the counter-clockwise direction. The position of the ball on the curve is defined by r(0(t)) = 1.2e0s(8(1)) m. Neglect friction and treat the ball as a particle. Find the magnitude of the the acceleration of the ball when & = 30deg, using the polar coordinate system