(2007? As shown in the figure, a smooth ring with a radius of R=0.50m is fixed on a vertical plane, and one end of the light spring is fixed at the highest point A of the ring.

(1) From B to C, the mechanical energy conservation of the system includes:

mg(R+Rcos60 )= 12mvc2+EPc？

Yes: vc=3mgR? 2EPCm=3×0.2× 10×0.5？ 2× 0.60.2 = 3m/s

(2) At point C, it can be obtained from Newton's second law: F+FN-mg=mvC2R.

Where: f = kr = 4.8× 0.5 = 2.4n

Replace: FN=3.2N

According to Newton's third law, the pressure of the ball on the ring is 3.2N, and the direction is vertical downward.

Answer: (1) The speed of the ball passing through point C is 3m/s. 。

(2) When the ball passes through point C, the force acting on the ring is 3.2N, and the direction is vertical downward.